Everything here builds on the core rules, arithmetic, and logarithms covered earlier in this site — this page is about applying them in the specific contexts a chemistry student or lab tech actually runs into. It also covers a genuinely surprising fact almost no other sig-figs resource mentions: for fourteen elements, there is no single “correct” atomic mass to plug into a calculation — the official value is a range, not because anyone’s measurement is imprecise, but because the atomic mass of these elements actually varies depending on where the sample came from. See Example 1.

Three Chemistry-Specific Rules

Molar mass: sum atomic masses using the addition rule, with atom counts as exact multipliers. A chemical formula’s subscripts (the “2” in H₂O, the “4” in CH₄) are exact counts of atoms — not measurements — so per our exact-numbers rule, multiplying an atomic mass by its subscript never reduces precision. What does limit precision is the atomic masses themselves: sum the (possibly multiplied) atomic masses using the ordinary addition rule — round the total to match the fewest decimal places among the values being summed. See Example 2.

pH: only the decimal places carry meaning, because pH is a logarithm. pH = −log₁₀[H⁺]. As established in our scientific notation guide, a logarithm’s mantissa (the decimal part) is what carries precision — the integer part just reflects order of magnitude. So the number of decimal places in a reported pH should match the number of significant figures in the concentration it came from — not the total digit count of the pH value. The same logic runs in reverse when converting a pH back to a concentration. See Examples 3 and 4.

Stoichiometry: mole ratios are exact; the measured quantity is the limit. The coefficients in a balanced chemical equation (the “2” in CH₄ + 2O₂ → CO₂ + 2H₂O) are exact, defined ratios — they never limit sig figs, no matter how the equation is written. The quantity that actually limits precision is whatever was measured: a given mass, volume, or concentration. Molar masses sit in between — they have their own real precision (see Example 1), but for a typical intro-level calculation, the measured starting quantity is usually the tightest constraint. As always, carry extra guard digits through intermediate mole calculations and round only the final answer. See Example 5.

Worked Examples

Example 1 — Atomic mass isn’t always a fixed number

Most sig fig guidance treats atomic mass as a known constant with obvious precision. It’s more interesting than that. The IUPAC body responsible for atomic weights (CIAAW) publishes the standard atomic weight of fourteen elements — including hydrogen, carbon, nitrogen, oxygen, and chlorine — as an interval, not a single value, because the true atomic mass genuinely varies with the terrestrial source of the sample. Hydrogen’s standard atomic weight is the interval [1.00784, 1.00811]; nitrogen’s is [14.00643, 14.00728]. For everyday calculation, CIAAW also publishes a single “abridged” conventional value for each — 1.0080 for hydrogen, for instance — which is what ends up printed on a classroom periodic table. The precision printed on your periodic table is itself a rounded, conventional choice, not an exact physical constant — which is exactly the kind of thing this site’s rule-attribution approach exists to make visible.

Example 2 — Molar mass with an exact multiplier

Calculate the molar mass of CH₄, using H = 1.008, C = 12.01 (standard 2-decimal-place classroom values).

4 × H = 4 × 1.008 = 4.032 — the “4” is an exact atom count, so this keeps all of 1.008’s precision (3 decimal places); no rounding happens at this step.

C + 4H = 12.01 + 4.032. Addition rule: match the fewest decimal places. 12.01 has 2, 4.032 has 3 — fewest is 2. Raw sum = 16.042 → round to 2 decimal places.

Answer: 16.04 g/mol.

Example 3 — pH from concentration

Calculate the pH of a solution with [H⁺] = 3.2 × 10⁻⁴ M (2 significant figures).

pH = −log₁₀(3.2 × 10⁻⁴) = −(0.505 − 4) = −(−3.495) = 3.49485…

Since [H⁺] has 2 sig figs, the pH should be reported to 2 decimal places — not 2 sig figs total. Rounding 3.49485 to 2 decimal places (the third decimal digit is 4, so round down):

Answer: pH = 3.49.

Example 4 — Concentration from pH (the reverse direction)

A solution has pH = 4.30 (2 decimal places). Find [H⁺].

[H⁺] = 10^(−pH) = 10^(−4.30) ≈ 5.012 × 10⁻⁵ M

Since the pH was given to 2 decimal places, [H⁺] should be reported to 2 significant figures — the reverse of Example 3’s rule, applied in the opposite direction.

Answer: [H⁺] = 5.0 × 10⁻⁵ M.

Example 5 — Full stoichiometry calculation

How many grams of CO₂ are produced from the complete combustion of 15.0 g of CH₄? Balanced equation: CH₄ + 2O₂ → CO₂ + 2H₂O. Molar mass CH₄ = 16.04 g/mol (Example 2). Molar mass CO₂ = 12.01 + 2(16.00) = 44.01 g/mol.

Moles of CH₄ = 15.0 g ÷ 16.04 g/mol = 0.93516… mol (guard digit kept, not yet rounded)

Mole ratio CH₄ : CO₂ is 1 : 1 — an exact ratio from the balanced equation, so it doesn’t touch the precision at all: moles of CO₂ = 0.93516… mol.

Mass of CO₂ = 0.93516… mol × 44.01 g/mol = 41.156… g (still unrounded)

Now round, once, at the very end — to 3 significant figures, matching the original 15.0 g (the tightest constraint in the whole calculation):

Answer: 41.2 g of CO₂.

Where This Still Trips People Up

• Different periodic tables print different precision, and that alone can shift a final answer’s last digit — a table rounded to whole numbers, one rounded to 2 decimal places, and IUPAC’s 5-sig-fig abridged values will not always agree past the first digit or two. This is one of the most common, and most innocent, reasons a “wrong” answer turns out to be a rounding-source mismatch rather than an actual error.
• Mole ratios are not measurements and never limit sig figs, but they’re routinely treated as if a “2” in a balanced equation had only 1 sig fig. It doesn’t — it’s exact, like every other stoichiometric coefficient.
• pH sig figs run backwards from the intuition most students bring in. A pH of 3.49 doesn’t have “3 sig figs” in the ordinary sense — its 2 decimal places correspond to 2 sig figs in the original concentration. Counting pH digits the normal way overstates the precision.
• Antilog conversions (pH → concentration) need the same care in reverse — see Example 4. It’s easy to remember the forward rule and forget it has a mirror image.
• “Exact” atomic mass isn’t quite the right mental model for the fourteen interval elements in Example 1 — even the conventional single-value numbers on a periodic table are themselves a rounded compromise, not a physical constant measured to arbitrary precision.

Precision Conventions by Source

There’s no single “correct” choice among these — the right move is to use whatever periodic table your course or exam actually provides, and expect a small final-digit mismatch against anyone using a different source. This is also the most common reason a calculator and a teacher disagree on a chemistry sig-fig answer without either one being wrong.

Where the Atomic Weight Data Comes From

The interval values in Example 1 come from CIAAW (the Commission on Isotopic Abundances and Atomic Weights), the IUPAC body that has published critical evaluations of atomic weights since 1902. Its most recent full report groups elements into those with well-documented natural isotopic variation (given as an interval), those limited by current measurement ability, and everything else (given as abridged 5-sig-fig values). This isn’t a chemistry-education simplification — it’s the literal reason a periodic table’s numbers look the way they do.

Common Mistakes

1. Treating a stoichiometric coefficient as if it limited sig figs. It’s exact — see Example 5.
2. Counting pH digits the normal way instead of matching decimal places to the concentration’s sig figs — see Example 3.
3. Forgetting the antilog direction has its own rule when converting pH back to concentration — see Example 4.
4. Rounding intermediate mole values during a multi-step stoichiometry calculation instead of carrying guard digits to the end — see Example 5.
5. Assuming a “wrong” chemistry answer is a calculation error when it’s actually a periodic-table-precision mismatch — see the comparison table above.
6. Multiplying an atomic mass by its subscript as if the subscript were a measured value, rather than recognizing it as an exact atom count that never limits precision.

Practice Problems

Concept: Molar mass with exact multipliers

Q1. Calculate the molar mass of H₂O (H = 1.008, O = 16.00). A) 18.0 g/mol B) 18.02 g/mol C) 18.016 g/mol D) 18.1 g/mol Answer: B) 18.02 g/mol (2 × 1.008 = 2.016, exact multiplier; 2.016 + 16.00 → round to 2 decimal places, matching O’s precision).

Q2. In calculating the molar mass of CO₂ (C = 12.01, O = 16.00), how many decimal places does the final answer have, and why? A) 3, matching the most precise atomic mass B) 2, matching the fewest decimal places among the summed terms C) 4, matching the total atom count D) 0, molar mass is always a whole number Answer: B.

Concept: pH from concentration

Q3. [H⁺] = 3.2 × 10⁻⁴ M (2 sig figs). What is the correctly reported pH? A) 3.5 B) 3.49 C) 3.494846 D) 3 Answer: B) 3.49.

Q4. Why does pH get reported with a number of decimal places (not total sig figs) matching the concentration’s sig figs? A) It’s an arbitrary convention B) Because pH is a logarithm, and only the mantissa carries precision — the integer part just reflects order of magnitude C) Because pH is always between 0 and 14 D) Because concentrations are always exact Answer: B.

Concept: Concentration from pH (antilog)

Q5. A solution has pH = 4.30 (2 decimal places). What is [H⁺], correctly rounded? A) 5.0 × 10⁻⁵ M B) 5.01 × 10⁻⁵ M C) 5 × 10⁻⁴ M D) 0.0000501 M Answer: A) 5.0 × 10⁻⁵ M.

Q6. If a pH is reported to 3 decimal places, how many significant figures should the corresponding [H⁺] have? A) 2 B) 3 C) 4 D) It depends on the specific pH value Answer: B) 3.

Concept: Exact mole ratios

Q7. In the balanced equation CH₄ + 2O₂ → CO₂ + 2H₂O, the coefficients (1, 2, 1, 2) are: A) Measured values with their own sig figs B) Exact numbers that never limit the calculation’s precision C) Approximate, typically to 1 sig fig D) Dependent on the amount of reactant used Answer: B.

Q8. 15.0 g of CH₄ (molar mass 16.04 g/mol) combusts completely. How many moles of CH₄ is this, correctly rounded? A) 0.9 mol B) 0.935 mol C) 0.93516 mol D) 0.94 mol Answer: B) 0.935 mol (3 sig figs, matching 15.0 g).

Concept: Full stoichiometry

Q9. Continuing Q8 (0.935 mol CH₄, a 1:1 mole ratio to CO₂, CO₂ molar mass 44.01 g/mol), how many grams of CO₂ are produced? A) 41 g B) 41.2 g C) 41.16 g D) 41.156 g Answer: B) 41.2 g.

Q10. Why is the final answer in Q9 limited to 3 significant figures, even though the molar masses used had 4? A) Molar masses are always ignored for sig fig purposes B) The originally given mass (15.0 g) has only 3 sig figs and is the least precise measured quantity in the whole calculation C) CO₂ is always reported to 3 sig figs D) The mole ratio limits it to 3 sig figs Answer: B.

One Element, Two Kinds of Number

Hydrogen:

• True standard atomic weight: an interval, [1.00784, 1.00811] — it genuinely varies by sample source
• Conventional abridged value (what’s printed on most periodic tables): 1.0080
• Common classroom rounding: 1.008 or 1.01

Nitrogen:

• True standard atomic weight: an interval, [14.00643, 14.00728]
• Conventional abridged value: 14.007
• Common classroom rounding: 14.01

Quick Reference

Continue Learning

Related fundamentals:

• Significant Figures: The Complete Guide
• Exact Numbers and Why They Never Limit Precision
• Significant Figures in Logarithms and pH

Go deeper on one chemistry topic at a time:

• Significant Figures in Stoichiometry Problems
• pH and Sig Figs: Why Only the Decimals Count
• Molar Mass: How Many Sig Figs Should You Use?
• Significant Figures in Titration Calculations
• Significant Figures Rules for AP Chemistry
• Significant Figures in IB Sciences (Internal Assessment)
• Significant Figures for GCSE and A-Level Sciences
• Why Your Teacher’s Sig Fig Answer Differs From the Calculator’s

Tools:

• Molar Mass & Stoichiometry Calculator
• Significant Figures Calculator

Sources and Further Reading

• CIAAW (Commission on Isotopic Abundances and Atomic Weights), Standard Atomic Weights 2024 — the current official table, including the fourteen elements published as intervals rather than single values, cited throughout Example 1. (ciaaw.org)
• CIAAW, Abridged Standard Atomic Weights 2024 — the conventional single-value, 5-significant-figure table most closely matching what appears on a printed periodic table. (ciaaw.org)
• Prohaska, T. et al., Standard atomic weights of the elements 2021 (IUPAC Technical Report), Pure and Applied Chemistry — the full technical report explaining why fourteen elements are given as intervals and how the abridged values are derived. (degruyterbrill.com)

Review and Methodology

Methodology: Atomic mass data is drawn directly from CIAAW’s current published tables (see Sources), not a secondary periodic table. Every worked example was independently recomputed during drafting. Calculator results referenced on this page use an arbitrary-precision decimal engine, not native floating-point math, validated against the site’s versioned regression fixture set.

Changelog

v1.0 — Initial draft completed, 2026-08-10.

The post Significant Figures in Chemistry: Stoichiometry, pH, and Molar Mass appeared first on SignificantFiguresCalculator.

Rule Statement

The molar mass of a compound is calculated by summing the atomic masses of its constituent atoms. The number of significant figures in the result is governed by the rules for addition: the result should have the same number of decimal places as the term with the fewest decimal places. However, when the molar mass is used as a conversion factor, it is treated as a measured quantity with its own uncertainty. In practice, the atomic masses are taken from a standard table, and the precision of those values determines the sig figs. The IUPAC standard atomic weights are given with uncertainties, but for most educational and routine work, molar masses are reported to 4 significant figures or to two decimal places. The rule: Use the atomic masses with the highest precision available, but do not report more sig figs than the least precise atomic mass in the formula.

Worked Examples

Example 1: Water (H₂O)

Atomic masses: H = 1.008 (4 sig figs), O = 16.00 (4 sig figs). Sum: 2(1.008) + 16.00 = 2.016 + 16.00 = 18.016. For addition, the decimal places: 1.008 has 3 decimal places, 16.00 has 2 decimal places, so the result should have 2 decimal places: 18.02 g/mol. This has 4 sig figs.

Example 2: Carbon Dioxide (CO₂)

C = 12.01 (4 sig figs), O = 16.00 (4 sig figs). Sum: 12.01 + 2(16.00) = 12.01 + 32.00 = 44.01. Both terms have 2 decimal places, so the result is 44.01 g/mol (4 sig figs).

Example 3: Sodium Chloride (NaCl)

Na = 22.99 (4 sig figs), Cl = 35.45 (4 sig figs). Sum: 22.99 + 35.45 = 58.44. Both have 2 decimal places, so the result is 58.44 g/mol (4 sig figs).

Counter-Examples

Common errors include using atomic masses with too many sig figs without applying the addition rule. For instance, using C = 12.011 and O = 15.9994 for CO₂ gives 12.011 + 2(15.9994) = 44.0098. The addition rule limits the result to 3 decimal places (since 12.011 has 3 decimal places), so the correct value is 44.010 g/mol, not 44.0098. Reporting 44.0098 with 6 sig figs is incorrect because the least precise atomic mass (C) has only 5 sig figs. Another error is treating atomic masses as exact numbers (e.g., C = 12) and reporting 44 g/mol, which loses significant precision.

Convention Comparison Table

Most educational contexts adopt the 4-sig-fig convention for simplicity and consistency. Always match the precision of your atomic mass source.

Standards Citation

Relevant standards for significant figures and rounding include:

• ASTM E29 – Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications. This standard outlines how to round test data.
• ISO 80000-1:2009 – Quantities and units, Part 1: General. Provides rules for expressing numerical values.
• NIST SP 811 – Guide for the Use of the International System of Units (SI). Contains guidance on significant figures and rounding.
• GUM (JCGM 100:2008) – Evaluation of measurement data – Guide to the expression of uncertainty in measurement. Emphasizes that the number of significant figures should reflect the uncertainty.
• IUPAC Technical Report on Standard Atomic Weights (e.g., 2021). Provides atomic weight values with uncertainties.

These standards emphasize that the reported value should not have more digits than the uncertainty justifies.

Common Mistakes

• Using atomic masses with too many sig figs without rounding the final result correctly.
• Ignoring the addition rule for decimal places when summing atomic masses.
• Treating atomic masses as exact numbers (e.g., C = 12) when they are measured quantities.
• Rounding intermediate values prematurely, leading to accumulated errors.
• Confusing significant figures with decimal places, especially when multiplying or dividing.

Practice Problems

1. Calculate the molar mass of H₂SO₄ using H = 1.008, S = 32.06, O = 16.00. Answer: 98.09 g/mol (4 sig figs).
2. Calculate the molar mass of Ca(OH)₂ using Ca = 40.08, O = 16.00, H = 1.008. Answer: 74.10 g/mol (4 sig figs).
3. Calculate the molar mass of C₆H₁₂O₆ using C = 12.01, H = 1.008, O = 16.00. Answer: 180.16 g/mol (4 sig figs).

Quick Reference Table

Related Rules

• Significant Figures in Addition and Subtraction
• Significant Figures in Multiplication and Division
• Rounding Methods: Half-Up, Half-Down, Banker’s
• Exact Numbers vs. Measured Quantities

The post Molar Mass: How Many Sig Figs Should You Use? appeared first on SignificantFiguresCalculator.

The pH scale is a logarithmic measure of hydrogen ion activity. By definition, pH = −log₁₀[H⁺], where [H⁺] is the molar concentration of hydrogen ions. Because pH is a logarithmic quantity, the integer part of the pH value (the characteristic) corresponds to the exponent of the concentration, while the decimal part (the mantissa) carries the precision of the measurement. Consequently, only the digits after the decimal point in a pH value are significant.

This rule is a direct consequence of the way logarithms transform numbers. A change of 1 pH unit represents a tenfold change in [H⁺]. For example, a pH of 3.00 corresponds to [H⁺] = 1.0 × 10⁻³ M, whereas a pH of 4.00 corresponds to [H⁺] = 1.0 × 10⁻⁴ M. The integer part (3 or 4) merely sets the order of magnitude; the decimal part (the .00) conveys the actual precision of the measurement. Thus, a pH of 3.00 has two significant figures (the two decimal places), not three.

This convention is universally adopted in analytical chemistry and is endorsed by standardization bodies. When reporting pH, the number of decimal places indicates the number of significant figures in the underlying concentration. For instance, a pH of 5.67 has two decimal places, meaning the hydrogen ion concentration is known to two significant figures (e.g., 2.1 × 10⁻⁶ M). The integer part (5) is not counted because it is an exponent placeholder.

Key Principle: The number of decimal places in a pH value equals the number of significant figures in the hydrogen ion concentration.

Worked Examples

Let us apply the rule with step-by-step reasoning.

Example 1: pH = 4.30

1. Identify the decimal places: pH has two digits after the decimal (3 and 0).
2. Therefore, the concentration [H⁺] should be reported with two significant figures.
3. Compute [H⁺] = 10⁻⁴·³⁰ = 5.0 × 10⁻⁵ M (rounded to two sig figs).
4. The pH value 4.30 indicates the concentration is known to ±0.005 × 10⁻⁵ M (i.e., the uncertainty is in the second decimal place of the mantissa).

Example 2: pH = 7.00

1. Decimal places: two (0 and 0).
2. Thus, [H⁺] has two significant figures: 1.0 × 10⁻⁷ M.
3. Note that the pH value itself has three digits, but only the two decimal places are significant.

Example 3: pH = 11.2

1. Decimal places: one (the digit 2).
2. Therefore, [H⁺] has one significant figure: 6 × 10⁻¹² M (since 10⁻¹¹·² ≈ 6.3 × 10⁻¹², rounded to one sig fig).
3. This pH is less precise than 11.20, which would have two decimal places and thus two sig figs in [H⁺].

Counter-Examples

Common mistakes arise when applying the usual significant figure rules to pH values. Here are typical counter-examples that highlight the errors.

Counter-Example 1: Treating all digits as significant

Incorrect: pH = 7.00 has three significant figures because there are three digits.

Correct: Only the two decimal places are significant. The integer 7 is an exponent placeholder. Reporting pH as 7.00 means the concentration is known to two significant figures (1.0 × 10⁻⁷ M). If you wanted three significant figures in concentration, you would need pH = 7.000 (three decimal places).

Counter-Example 2: Rounding the integer part

Incorrect: Rounding pH 9.87 to 10 (one decimal place) because 9.87 rounds to 10.0? Actually, rounding to one decimal place gives 9.9, but the integer part changes when rounding to a whole number. However, the integer part is not subject to significant figure rounding; it is the exponent. Rounding pH 9.87 to 10 would be absurd because it would imply a concentration of 1 × 10⁻¹⁰ M, which is a factor of 10 off from 1.3 × 10⁻¹⁰ M. Always keep the decimal places intact.

Counter-Example 3: Using sig figs in pH for addition/subtraction

Incorrect: When averaging pH values, you apply addition/subtraction rules based on decimal places. That is actually correct for pH because pH is a logarithmic quantity, and the uncertainty is in the decimal places. But some mistakenly apply multiplication/division rules (counting total sig figs). For example, averaging pH 4.5 and 4.7: the result should be 4.6 (one decimal place), not 4.60 (which would imply two decimal places of precision).

Convention Comparison Table

This table underscores that the same written number (e.g., 3.45) can have different significant figure interpretations depending on whether it is a pH or a direct measurement.

Standards Citation

The convention is rooted in international standards and metrology guidelines. The International Union of Pure and Applied Chemistry (IUPAC) in its Quantities, Units and Symbols in Physical Chemistry (the Green Book, 3rd ed., 2007) defines pH as a logarithmic quantity and states that “the number of decimal places in the pH value indicates the number of significant figures in the hydrogen ion activity.” Similarly, ISO 80000-8:2007 (Quantities and units – Part 8: Acoustics) and more directly ISO 80000-9:2019 (Physical chemistry and molecular physics) address logarithmic quantities, emphasizing that the characteristic (integer part) is not significant.

In the United States, NIST (National Institute of Standards and Technology) provides guidance in its Guide to the Expression of Uncertainty in Measurement (GUM, JCGM 100:2008) and in specific pH measurement protocols. NIST Technical Note 1297 (1994) on evaluating and expressing uncertainty explicitly states that for quantities expressed as logarithms, the uncertainty is in the mantissa, and the number of decimal places should reflect the measurement precision.

For industrial and laboratory practice, ASTM E29-13 (Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications) provides general rules for rounding, but it does not override the logarithmic convention. The pH-specific rule is widely taught in analytical chemistry textbooks and is consistent with the GUM principle that the reported uncertainty must match the resolution of the measurement.

Common Mistakes

• Counting the integer part: Assuming pH 5.00 has three sig figs. Always count only decimal places.
• Rounding pH to a whole number: Reporting pH as 7 instead of 7.00 loses all precision and is acceptable only if the concentration is known to one order of magnitude.
• Applying multiplication/division sig fig rules to pH: When converting pH to [H⁺], you use the inverse log, which is an exponentiation operation. The number of sig figs in the result is determined by the number of decimal places in the pH, not by the total number of digits.
• Using pH in arithmetic without adjusting decimal places: For example, adding pH values is not meaningful; you must convert to concentrations first. When averaging pH values, the result should be rounded to the same number of decimal places as the least precise pH.
• Ignoring trailing zeros: A pH of 4.50 has two decimal places, so it is more precise than 4.5 (one decimal place). Trailing zeros after the decimal point are significant in pH.

Practice Problems

Test your understanding with these exercises.

1. How many significant figures are in the concentration [H⁺] if pH = 8.32?
2. If a pH meter reads 5.0, what is the uncertainty in [H⁺]?
3. Convert pH = 10.45 to [H⁺] and report with the correct number of significant figures.
4. Which pH value is more precise: 3.2 or 3.20? Explain.

Answers:

1. Two decimal places → 2 sig figs in [H⁺].
2. One decimal place → [H⁺] = 1 × 10⁻⁵ M (one sig fig), so uncertainty is roughly ±0.5 × 10⁻⁵ M.
3. 10.45 has two decimal places → [H⁺] = 3.5 × 10⁻¹¹ M (two sig figs).
4. 3.20 is more precise because it has two decimal places, indicating [H⁺] known to two sig figs, whereas 3.2 has one.

Quick Reference Table

Use this table as a quick reference when reporting pH values. Remember: the decimal places are your significant figures.

Sources & Further Reading

• IUPAC. Quantities, Units and Symbols in Physical Chemistry (Green Book), 3rd ed., 2007.
• ISO 80000-9:2019. Quantities and units – Part 9: Physical chemistry and molecular physics.
• NIST. Guide to the Expression of Uncertainty in Measurement (GUM), JCGM 100:2008.
• ASTM E29-13. Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications.
• Harris, D.C. Quantitative Chemical Analysis, 9th ed., W.H. Freeman, 2016 (Chapter on pH and significant figures).

For more precision and rounding resources, explore our significant figures calculator and other articles on logarithmic quantities.

The post pH and Sig Figs: Why Only the Decimals Count appeared first on SignificantFiguresCalculator.