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Limiting Reactant Calculator | Find limiting reactant by amounts

Identify which reactant runs out first in any chemical reaction, how much excess remains, and the theoretical yield it produces. Enter the masses and balanced-equation coefficients and the tool walks through the mole comparisons — a must-have for stoichiometry.

Last updated: June 2026 · Free · No sign-up required

Results

Enter values above and click Calculate to see your result instantly.

Quick reference

ReactantMoles ÷ coefficient
Amoles of A ÷ coefficient of A
Bmoles of B ÷ coefficient of B
Limitingthe reactant with the smaller ratio
Excessthe reactant with the larger ratio

info Limiting Reactant Calculator

Free math calculator — enter your numbers and get an instant, accurate result.

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Everything runs locally in your browser. No uploads, no accounts, no tracking.

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info Educational

Includes the formula and step-by-step explanation so you understand the math, not just the answer.

Interpretation guide

OutputWhat it tells you
Limiting reactantRuns out first and caps the product yield.
Excess reactantSome is left over when the reaction finishes.
RatiosThe mole-to-coefficient ratio for each reactant.

lightbulb Worked example

Let's say you are using the Limiting Reactant Calculator. Limiting Reactant Calculator is a free online calculator that helps you work out limiting reactant quickly and accurately, right in your browser. Enter the values that match your situation into the input fields and press calculate — using realistic numbers makes the result directly useful for you.

Result: The calculator instantly applies the formula Compare moles ÷ coefficient for each reactant; the smaller ratio is limiting and returns the result with appropriate precision.

What this means: Read the result in the context of what you are measuring. The step-by-step breakdown lets you confirm the math and understand which input most affects the outcome.

Formula & methodology

Formula: Compare moles ÷ coefficient for each reactant; the smaller ratio is limiting

The Limiting Reactant Calculator is built on a well-established calculation method. It uses the formula Compare moles ÷ coefficient for each reactant; the smaller ratio is limiting to turn your inputs into a reliable result. Limiting Reactant Calculator is a free online calculator that helps you work out limiting reactant quickly and accurately, right in your browser. The steps are shown on the page so you can follow the reasoning from input to output.

The limiting reactant is the one that runs out first. Divide each reactant's moles by its balanced equation coefficient; the smallest ratio identifies the limiting reactant.

  1. Balance the equation and note each reactant's coefficient.
  2. Enter the moles and coefficient for reactant A and reactant B.
  3. The calculator computes moles ÷ coefficient for each.
  4. The smaller ratio is the limiting reactant; the other is in excess.

Worked example: 3 mol A (coeff 1) gives ratio 3; 2 mol B (coeff 3) gives 0.67, so B is limiting.

Authoritative source: Wolfram MathWorld

Frequently asked questions

How do I find the limiting reactant?
Enter the required values into the input fields and press the calculate button. The tool applies the formula Compare moles ÷ coefficient for each reactant; the smaller ratio is limiting and returns the result with a short explanation of each step, so you can check the working yourself.
Why do I need the coefficients?
The Limiting Reactant Calculator is free, private, and accurate: it runs entirely in your browser (no uploads, no accounts), applies the standard calculation, and explains each step so you can verify the result. Limiting Reactant Calculator is a free online calculator that helps you work out limiting reactant quickly and accurately, right in your browser. There is no limit on usage, and it works on any device.
What is the excess reactant?
The excess reactant is the reagent left over after the reaction completes, because more of it was supplied than the balanced equation requires. Its remaining amount is the initial quantity minus what the limiting reactant consumed. The calculator shows which reactant is in excess and how much remains, which matters for cost control and for isolating products without unreacted material.
Does the limiting reactant set the yield?
Yes — the limiting reactant determines the theoretical yield, because the reaction stops when it is fully consumed, regardless of how much excess remains. Doubling the limiting reactant (up to the excess available) roughly doubles the product; adding more excess reactant changes nothing. This is why identifying the limiter is the first step in every yield calculation.
Is it free and private to use?
Yes — the Limiting Reactant Calculator. There is no sign-up, no paywall, no trial, and no limit on how many calculations you can run. CalcaTools covers its costs with non-intrusive display advertising, so the calculator itself never asks for payment or restricts any feature.
What does the Limiting Reactant Calculator do?
Limiting Reactant Calculator is a free online calculator that helps you work out limiting reactant quickly and accurately, right in your browser. The calculator takes your inputs, applies the standard calculation, and returns a clear result so you can make an informed decision without doing the math by hand.
What formula does the Limiting Reactant Calculator use?
The Limiting Reactant Calculator applies the standard formula: Compare moles ÷ coefficient for each reactant; the smaller ratio is limiting. The tool walks through each step of the calculation so you can verify the numbers yourself.
Is the Limiting Reactant Calculator free and private?
Yes — it is free with no sign-up or usage limits, and every calculation runs in your browser so no data is uploaded. CalcaTools supports itself with display ads. The tool identifies the limiting reactant, the excess remaining, and the theoretical yield; for safety-critical chemistry, always verify with your own stoichiometry and lab supervision.
How accurate is the Limiting Reactant Calculator?
The Limiting Reactant Calculator applies the standard formula: Compare moles ÷ coefficient for each reactant; the smaller ratio is limiting. It is tested against published worked examples before launch and uses native double-precision arithmetic, so results are accurate to typical precision for the values you enter — with no intermediate rounding that could distort the answer.

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