Chemical Equation Balancer & Molar Mass

Type an unbalanced equation such as C3H8 + O2 = CO2 + H2O to get the smallest whole-number coefficients with an atom-by-atom check, or type a formula such as CuSO4·5H2O to get its molar mass with each element's share, and convert between grams and moles.

Free, no signupNo daily limitRuns in your browser - nothing you enter is uploadedUpdated 7 October 2026

Unbalanced equation

Worked example: burning propane

C₃H₈ + O₂ → CO₂ + H₂O, with unknown coefficients a, b, c, d:

Carbon: 3 on the left per propane3a = c
Hydrogen8a = 2d
Oxygen2b = 2c + d
Set a = 1 and solvec = 3, d = 4, b = (6 + 4) ÷ 2 = 5
BalancedC3H8 + 5O2 → 3CO2 + 4H2O

Check: C 3 = 3, H 8 = 8, O 10 = 6 + 4.

Why it uses algebra, not guesswork

By hand you balance by trial and error. That works for small equations but gets slow when an element appears in several compounds, as in KMnO₄ + HCl. This balancer writes the conservation of every element as an equation, exactly as in the worked example, and solves the whole system at once with exact fractions. The result is then scaled to the smallest whole numbers, so 2, 16, 2, 2, 8, 5 is found directly rather than by guessing.

Molar mass

The molar mass of a compound is the sum of its atoms' atomic masses in grams per mole. For copper(II) sulfate pentahydrate, CuSO₄·5H₂O: Cu 63.546 + S 32.06 + 9 O × 15.999 + 10 H × 1.008 = 249.677 g/mol. The breakdown table shows each element's share of the mass, which is how percentage composition questions are answered.

What this calculator does not do

Neutral species only: ionic equations with charges and electrons (redox half-equations) are not supported.
Elements 1 to 95 (hydrogen to americium).
It balances atoms; it cannot tell whether a reaction actually happens or predict the products.

Frequently asked questions

How does the balancer work?

It counts each element in each substance and writes one equation per element saying atoms on the left equal atoms on the right. Solving that system exactly gives the ratio of coefficients, which is then scaled to the smallest whole numbers.

How do I type formulas?

Use element symbols with the correct capitals (NaCl, not nacl), numbers for subscripts (H2O), brackets for groups (Ca(OH)2, [Cu(NH3)4]SO4) and a dot for hydrates (CuSO4·5H2O or CuSO4.5H2O). Separate substances with + and the two sides with =, -> or →.

Why does it say an equation can't be balanced?

Either an element appears on only one side, which usually means a formula is mistyped, or the reaction has no balance with all coefficients positive. Check each formula carefully.

What does "more than one independent way" mean?

Some equations combine two separate reactions, so there are many valid sets of coefficients with no single correct answer. Split it into the individual reactions and balance each one.

Which atomic masses are used?

The standard atomic weights published by IUPAC, abridged to four or five significant figures - for example C 12.011, O 15.999 and Cl 35.45. Radioactive elements with no stable isotopes, such as technetium, use the mass number of their longest-lived isotope.

How do I convert grams to moles?

Divide the mass in grams by the molar mass: moles = grams ÷ g/mol. 36.03 g of water is 36.03 ÷ 18.015 = 2.000 mol. The molar mass tab does this for you.

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Step-by-step guide: How to balance chemical equations →

Built and checked by Taimur Hassan Siddiqui, who has more than ten years in computer-science education. The formulas on this page are covered by an automated test suite, and the worked example on this page is one of its cases. Last updated 7 October 2026.