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Limiting Reactant Calculator

Enter the chemical equation, click “Calculate”, and add the known amount of each reactant to find the limiting reactant with this tool.

H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg TI Pb Bi Po At Rn
Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Cn Nh FI Mc Lv Ts Og
SPACE Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
CLEAR Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Your Input 1 2 3 4 5 6 7 8 9 0 + = Compound

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Limiting Reactant Calculator:

The limiting reactant calculator works to calculate the limiting reactant in a chemical reaction. It balances the chemical equation and shows the reactants and products along with their coefficients. Then, by adding values of reactants, it identifies the limiting reagent that is completely consumed and the maximum amount of product that can be formed based on the limitations.

What Is A Limiting Reactant?

In a chemical reaction, the limiting reactant is the reactant that gets completely consumed, limiting the amount of final product (also called yield) that can be formed. The limiting reactant can be determined with the help of the stoichiometry of the balanced chemical equation. A stoichiometry refers to the balanced chemical equation that indicates the relative ratios of reactants required to react completely and to form the product. 

How To Find Limiting Reactant?

1. Balance The Chemical Equation:

It is necessary to have a balanced chemical equation for the reaction. A balanced equation contains the reactants (starting materials) on the left side and the products (formed substances) on the right side, with coefficients showing their quantities. You must balance your chemical reaction to highlight the limiting reactant before going further. 

For example, in an equation like:

H2 + O2 =H2O

Balanced Equation: 2 H2 + O2 -> 2 H2O

2. Identify Mole Ratios:

The coefficients in the balance equation represent the mole ratios of reactants and the products that are formed. In the above example, the mole ratio of H2 to O2 is 2:1, meaning 2 moles of H2 react with 1 mole of O2 to form 2 moles of H2O.

3. Convert Quantities (to moles):

If you have information about the initial amounts of reactants (mass, volume), you can convert them to moles using their molar masses or molar volumes (for gases). This allows you to compare them directly using mole ratios.

4. Compare Reactant Quantities (or Mole Ratios):

  • Without Initial Quantities: Compare the mole ratios, the reactant that has the smallest ratio is called the limiting reactant 
  • With Initial Quantities: Divide the amount (in moles) of each reactant by its mole ratio from the balanced equation. The reactant that has the smallest result after division is the limiting reactant


Let's suppose, you react propane (C3H8) and oxygen (O2) to produce carbon dioxide (CO2) and water (H2O), given 5 moles of propane and 8 moles of oxygen. Now find the limiting reactant and the amount of CO2 produced.


Step #1: Balanced Chemical Equation

The balanced chemical equation for this reaction is:

C3H8 + 5O2 -> 3CO2 + 4H2O

It shows that 1 mole of Propane (C3H8) reacts with 5 moles of Oxygen (O2) to produce 3 moles of Carbon Dioxide (CO2) and 4 moles of Water (H2O).

Step #2: Mole Ratios

  • Propane (C3H8) to Oxygen (O2) = 1:5 (1 mole C3H8 reacts with 5 moles O2)
  • Propane (C3H8) to Carbon Dioxide (CO2) = 1:3 (1 mole C3H8 produces 3 moles CO2)

Step #3: Convert Quantities to Moles

We are given the initial quantities of the reactants in moles:

  • Propane (C3H8): 5 moles
  • Oxygen (O2): 8 moles

Step #4: Compare Reactant Quantities

Divide the initial moles of each reactant by its corresponding mole ratios:

Propane (C3H8): Moles (ratio to O2)

Propane (C3H8): 5 1

Propane (C3H8) = 5 moles

Oxygen (O2): Moles (ratio to C3H8)

Oxygen (O2): 8 5

Oxygen (O2) = 1.6 moles

Analyze The Results:

If all the Propane (4 moles) is used based on its mole ratio, it will require 5 moles x 5 (ratio) = 25 moles of Oxygen. But we only have 8 moles of Oxygen which will be used up before all the Propane reacts.

Limiting Reagant = Oxygen (O2)

Apart from these steps, the limiting reactant finding process can be automated with the use of our limiting reactant calculator.

Why Limiting Reactants Important?

  • Predicting Product Yield: By identifying the limiting reactant, you can calculate the theoretical yield, which is the maximum amount of product that can be formed based on the available limiting reactant. It is very useful in planning experiments and optimizing processes
  • Optimizing Reactions: Knowing the limiting reactant allows you to use your starting materials more efficiently. You can adjust the initial quantities of reactants to minimize waste and maximize the desired product
  • Understanding Reaction Stoichiometry: Limiting reactants helps you bridge the gap between the balanced chemical equation (theoretical) and a real-world reaction (practical). For instance, you have a specific amount of ingredients. Now with the help of limiting reactant, you can understand how many cookies you can bake even when you have an excess amount of some ingredients
  • Environmental Chemistry: The limiting reactants help assess what limits the breakdown of pollutants in the environment. This knowledge is used to design strategies for remediation, like adding the missing element to accelerate the breakdown of a pollutant


Can There Be A Limiting Reagent If Only One Reactant Is Involved In The Reaction?

No, there can’t be a limiting reagent if only one reactant is involved in the chemical reaction. The limiting reactant is the situation where multiple reactants are involved in a reaction. 

What Is The Limiting Reactant Used To Calculate?

The limiting reactant is used to find the amount of product that can be obtained from a reaction in which reactants are involved in a specific quantity. 

Is Limiting Reactant Always The Same For Given Chemical Reaction?

Yes, for a specific reaction where the initial reactants are given, the limiting reactant will remain the same. You can use the limiting reagent calculator to analyze the reaction by identifying the limiting reactant.


From the source of Wikipedia: Limiting reagents, Comparison, Comparison of product amounts.

From the source of Khan Academy: Limiting reactant, Reaction yields, Stoichiometry. 

From the source of Lumen Learning: Limiting Reagents, Chemical Reactions.

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