Excess Reactant Calculator
Find the excess reactant and leftover amount.
About Excess Reactant Calculator
Finding the limiting reactant for Excess Reactant compares what each reactant demands of the other; the one that falls short is the limit, and the other leaves excess behind. The limiting reactant determines the maximum product, so it is the bottleneck of every yield calculation.
Formula
Excess Reactant
Compare reactant 2 needed (r1 x ratio) against reactant 2 available
- limiting reactant
- The reactant that runs out first and caps the product
Worked example
With the default values below, Excess Reactant Calculator returns Limiting Reactant of Reactant 2 is limiting. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Reactant 1 molesminimum 0
- 2
- Reactant 2 molesminimum 0
- 1.5
- Stoichiometric ratiominimum 0
- 1
Results
- Limiting Reactant
- Reactant 2 is limiting
- Excess Moles Left
- 0.500 mol
- Product Moles
- 1.500 mol
Step by step
- 1Values used
- 2Excess Reactant
- 3Limiting Reactant= Reactant 2 is limiting
- 4Excess Moles Left= 0.500 mol
- 5Product Moles= 1.500 mol
Assumptions and limits
- The result is derived only from the 3 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 3 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
How is Excess Reactant calculated?
Compare reactant 2 needed (r1 x ratio) against reactant 2 available Finding the limiting reactant for Excess Reactant compares what each reactant demands of the other; the one that falls short is the limit, and the other leaves excess behind.
Why does Excess Reactant matter?
The limiting reactant determines the maximum product, so it is the bottleneck of every yield calculation.
What values do I need to enter?
This calculator takes 3 inputs: Reactant 1 moles, Reactant 2 moles, Stoichiometric ratio. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.