Stoichiometry Calculator Chemistry tools
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Stoichiometry calculator: limiting reagent, theoretical yield, and percent yield

Calculate the limiting reagent, excess amount, theoretical yield, and percent yield from reaction coefficients and inputs such as g, mol, and solution M × L.

This page performs calculations only; it does not provide procedures, conditions, or safety guidance.

Uses explicit, user-entered coefficients Accepts g, mol, and solution M × L inputs Shows excess amount, theoretical yield, and percent yield together Supports share URLs and local auto-save
Choose an example; the same setup will load when you open the tool.
Selected example
Choose an example to preview its reaction and sample quantities here.
This page performs calculations only. It does not cover reaction procedures, conditions, safety, equipment, or hazard assessment.
Real reactions can differ from theory because of side reactions, equilibrium, solubility, kinetics, and handling loss.
Enter the coefficients yourself; automatic balancing is not provided.

Stoichiometry in practice: limiting reagent, theoretical yield, and percent yield

Stoichiometry links reaction coefficients with the amounts you enter. It identifies the reactant that runs out first, estimates product formation, and compares actual results with the theoretical maximum.

Inputs required by the calculator

Enter coefficients for reactants and products, reactant amounts, and—when needed—molar masses and yield data.

How the limiting-reagent calculation works

For each reactant, divide its amount in mol by its coefficient. The smallest quotient identifies the limiting reagent.

How to interpret percent yield

Theoretical yield is the ideal maximum without loss or side reactions. Percent yield compares the actual amount with that theoretical value.

How to use the calculator

  1. Load an example or enter reactant and product coefficients, names, and any required molar masses.
  2. For each reactant, enter a mass, amount of substance, or solution input (M × L).
  3. If needed, choose a target product and enter an expected or actual yield.
  4. Calculate to review the limiting reagent, excess amount, theoretical yield, yield values, and calculation details.

Examples

Water formation

Input

2 H2 + O2 → 2 H2O, H2 4 g, O2 32 g

Output

H2 is limiting and the theoretical yield of H2O is about 35.7 g

Ammonia synthesis

Input

N2 + 3 H2 → 2 NH3, N2 28 g, H2 6 g

Output

H2 is limiting and the tool shows both the theoretical NH3 yield and the excess N2

Abstract ratio example

Input

A + 2 B → C, A 1 mol, B 1 mol

Output

B is limiting and C is 0.5 mol

How the limiting reagent is calculated (with an example)

How to interpret a limiting-reagent calculation

The calculator divides each reactant amount in mol by its coefficient. The smallest quotient identifies the limiting reagent. When quotients are nearly equal, it also warns about a possible co-limiting case.

How percent yield is calculated (expected versus actual yield)

A common source of confusion in yield calculations

Expected yield is a planning estimate; actual yield is observed after the reaction or process. The tool keeps them separate so they are not confused.

Frequently asked questions

Can the tool balance a chemical equation automatically?

Not yet. Enter the coefficients yourself so the quantitative assumptions remain explicit.

Can it calculate from solution inputs (M × L)?

Yes. It converts concentration × volume into mol before applying the reaction ratio.

Can I use it for multistep reactions?

For now, calculate each step separately. A linked multistep workflow may be added later.

Which product does the yield refer to when there are multiple products?

Yield is normally reported for one target product. Select that product here.

How should I account for reagent purity or assay?

Enter purity as a percentage; the calculator adjusts the effective input amount in mol.

Glossary

Limiting reagent

The reactant consumed first, which therefore limits the reaction extent.

Theoretical yield

The maximum amount predicted when no side reaction or process loss occurs.

Percent yield

Actual yield divided by theoretical yield, expressed as a percentage.

Extent of reaction ξ

A quantity describing how far the reaction proceeds and linking coefficients to mol calculations.

Calculation formulas

  • Mass to amount: n = m / M
  • Solution to amount: n = C × V
  • Limiting reagent: ξ = min(nᵢ / νᵢ)
  • Product amount: n_product = ν_product × ξ
  • Percent yield = actual ÷ theoretical × 100

Notes

  • Any error in molar mass, coefficient, or purity feeds directly into the result.
  • Remaining solution is shown as supply-equivalent volume, not the true volume of the mixed solution left.
  • Substance names appear in the share URL; do not enter confidential names.