Limiting Reagent Calculator

Work out limiting reagent instantly with clear inputs, formula shown and shareable results.

About Limiting Reagent Calculator

The limiting reagent is not simply the one present in the smallest amount - it is the one with the smallest moles-per-coefficient. Dividing each reagent's moles by its balancing coefficient gives how many times the reaction can run on that reagent alone, and the smaller figure caps the reaction. With 3 mol of A at coefficient 1 and 5 mol of B at coefficient 2, B allows only 2.5 runs against A's 3, so B limits.

Formulas

Extent available per reagent

extent = moles / coefficient

Reaction extent

extent = min(extent A, extent B)

Worked example

With the default values below, Limiting Reagent Calculator returns Reaction Extent of 2.5000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Moles of reagent Aminimum 0 mol: 3 mol
Stoichiometric coefficient of Aminimum 0: 1
Moles of reagent Bminimum 0 mol: 5 mol
Stoichiometric coefficient of Bminimum 0: 2

Results

Reaction Extent: 2.5000 mol
Limiting Reagent: Reagent B
Excess Reagent Left Over: 0.5000 mol
Availability Ratio A:B: 1.2000

Step by step

1Values used
2Extent available per reagent
3Reaction extent
4Reaction Extent= 2.5000 mol
5Limiting Reagent= Reagent B
6Excess Reagent Left Over= 0.5000 mol
7Availability Ratio A:B= 1.2000

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why divide by the coefficient?

Because a reagent consumed two at a time runs out twice as fast. Raw mole counts ignore that and pick the wrong limiter.

What does reaction extent mean?

The number of times the balanced equation as written can proceed. Multiply it by any product coefficient to get that product's moles.