Advanced Reaction Stoichiometry Calculator

Calculator Inputs

Reaction or Scenario Title

Reactant A Name

Coefficient A

Molar Mass A (g/mol)

Amount A

Unit A

Purity A (%)

Reactant B Name

Coefficient B

Molar Mass B (g/mol)

Amount B

Unit B

Purity B (%)

Product Name

Product Coefficient

Product Molar Mass (g/mol)

Product Output Unit

Process Efficiency (%)

Actual Yield (optional)

Actual Yield Unit

Gas volume inputs assume standard conditions of 22.4 L/mol. Enter balanced coefficients before calculating.

Example Data Table

Reaction	Input A	Input B	Limiting Reagent	Theoretical Product	Leftover Excess
2 H2 + O2 → 2 H2O	10 g H2, 100% purity	40 g O2, 100% purity	O2	45.0375 g H2O	4.9600 g H2
N2 + 3 H2 → 2 NH3	28 g N2, 95% purity	8 g H2, 100% purity	N2	32.2500 g NH3	5.1304 g H2
CaCO3 → CaO + CO2	100 g CaCO3, 98% purity	Not needed	Single-reactant setup	54.9180 g CaO	Unreacted impurity remains

The built-in defaults use the first example so you can test the calculator immediately.

Formula Used

1) Convert input to moles

n = m / M

n = N / N_A

n = V / 22.4

Where n is moles, m is mass, M is molar mass, N is particle count, and V is gas volume at STP.

2) Correct for purity

n_usable = n × purity / 100

3) Determine reaction extent

extent = min(n_A/a, n_B/b)

4) Find theoretical product

n_product = extent × c

5) Convert product moles to selected output

mass = n × M

6) Calculate percent yield

% yield = actual / theoretical × 100

How to Use This Calculator

Enter a descriptive title for the reaction or experiment.
Type the two reactants and one target product.
Add balanced stoichiometric coefficients from the chemical equation.
Enter molar masses for each substance.
Choose each reactant input unit and enter the amount.
Adjust purity percentages for impure feed materials.
Select the desired product output unit.
Optionally enter process efficiency and actual yield.
Press Calculate Stoichiometry to show results above the form.
Use the CSV or PDF buttons to save the calculation summary.

Frequently Asked Questions

1. What does a reaction stoichiometry calculator do?

It converts reactant amounts into moles, compares stoichiometric ratios, identifies the limiting reagent, estimates theoretical yield, and reports leftover excess material.

2. Why are balanced coefficients required?

Stoichiometric relationships come directly from the balanced chemical equation. Wrong coefficients produce wrong limiting reagent, yield, and excess calculations.

3. How does purity affect the result?

Purity reduces the chemically available portion of a reactant. A 90% pure sample contributes only 90% of its converted mole amount to the reaction.

4. What is the limiting reagent?

The limiting reagent is the reactant that runs out first according to stoichiometric ratios. It caps the maximum possible amount of product.

5. What is theoretical yield?

Theoretical yield is the maximum product predicted from stoichiometry when the limiting reagent reacts completely and no side losses occur.

6. What units can I enter?

You can enter grams, moles, particles, or liters at STP. The calculator converts each value to moles before comparing stoichiometric ratios.

7. Why is actual yield optional?

Actual yield is only needed when you want percent yield. If omitted, the calculator still reports limiting reagent, theoretical yield, and excess reactant leftovers.

8. Can I use this for gases?

Yes. Gas volume entries are supported at standard conditions using 22.4 liters per mole. For non-STP conditions, convert externally first.