Four calculators, one panel.
Pick a mode below — enter any chemical formula, everything recalculates live as you type, and every result explains itself.
Use standard notation — parentheses like Ca(OH)2, and a dot for hydrates like CuSO4·5H2O.
Give it in grams (or mg/kg) to get moles back, or in moles (or mmol/kmol) to get mass back.
Leave the formula blank to skip the theoretical-yield calculation.
The maximum amount the balanced equation predicts.
What you actually recovered, in the same unit as above.
Two or three inputs to an answer.
No manual required — but here's the entire flow in four moves.
Pick a mode
Molar mass for any formula on its own. Mole-mass to convert grams and moles. Limiting reactant for a balanced equation with two reactants. Percent yield to compare actual and theoretical results.
Enter the formula & numbers
Type a chemical formula using standard capitalisation and pick the unit from the dropdown next to each amount — grams, milligrams, kilograms, or moles all convert automatically. The example chips fill everything in with one tap.
Read the results
The main answer sits up top in large type. Related values — other units, particle counts, or the excess reactant — sit below, and the exact formula with your numbers substituted sits at the bottom.
Trust the checks
Invalid formulas, unknown elements, negative amounts, or a zero you're trying to divide by get flagged with a plain-English reason instead of a wrong or broken answer. Copy any result set with one click.
Three relationships, one calculator.
Every mode above comes down to one of these three ideas.
Molar mass
Add up each element's atomic mass multiplied by how many times it appears in the formula, including inside parentheses and hydrate groups.
Mole ↔ mass
Moles (n) equal mass (m) divided by molar mass (M) — and mass equals moles times molar mass, the same relationship read the other way.
Limiting reactant & yield
Divide each reactant's moles by its coefficient in the balanced equation — the smaller ratio is limiting, and it sets the theoretical yield of product.
Questions people actually ask.
The short answers — with the long ones one tap away.
What is stoichiometry?+
Stoichiometry relates the amounts of reactants and products in a chemical reaction. It uses molar mass to convert between grams and moles, and the coefficients of a balanced equation to convert between moles of one substance and moles of another.
How do I calculate molar mass from a chemical formula?+
Enter a formula such as H2O, Ca(OH)2 or CuSO4·5H2O in the Molar mass tab. The calculator reads every element and subscript — including parentheses and hydrate dots — multiplies each atomic mass by its count, and adds the results in g/mol.
How do I convert grams to moles, or moles to grams?+
Enter the formula and known amount in the Mole-mass tab: n = m ÷ M, and m = n × M. The molar mass is worked out automatically, and the calculator also shows the number of particles using Avogadro's number.
How do I find the limiting reactant?+
Enter both reactants' formulas, amounts, and balanced-equation coefficients in the Limiting reactant tab. Each amount is converted to moles and divided by its coefficient — whichever gives the smaller value is limiting. The calculator then reports the leftover excess and the theoretical yield of the product.
What is percent yield and how do I calculate it?+
Percent yield compares what you actually collected to the maximum theoretical amount: % yield = actual ÷ theoretical × 100. Enter both values in the Percent yield tab, in the same unit, to get the result instantly.
Does this calculator balance chemical equations for me?+
No — enter the coefficients from an equation you've already balanced. The Limiting reactant tab uses those coefficients to work out mole ratios, so make sure the equation is balanced first.
Is this tool free, and where does my data go?+
It's completely free and runs entirely in your browser — nothing you type is uploaded, logged, or sent to any server. No account, no sign-up, no limits.