Theoretical Yield Calculator
Find the maximum product mass from the limiting reactant.
Results update as you type.
How it works
Theoretical yield is the maximum amount of product a chemical reaction can possibly produce, and this calculator finds it from the limiting reactant. You enter the moles of the limiting reactant, the mole ratio between the product and that reactant taken from the balanced equation, and the molar mass of the product; the calculator returns the product in both moles and grams. The limiting reactant is the one that runs out first and therefore caps how much product can form, no matter how much of the other reactants is present. Calculating theoretical yield is an essential step before running or scaling a reaction, because it tells you the best possible outcome against which the actual yield is compared to judge efficiency. Chemists use it to plan how much starting material to use, to predict product quantities, and to compute percent yield afterward. The calculation assumes the reaction proceeds completely and cleanly, which real reactions never quite do, so the actual yield is always somewhat lower. To use it, first identify the limiting reactant and its moles, read the product-to-reactant ratio from the balanced equation, and supply the product's molar mass. Enter the three values to get the theoretical yield.
product moles = moles limiting × mole ratio; yield = product moles × molar mass
The theoretical yield is the most product a reaction can make, set entirely by the limiting reactant. Multiplying the moles of limiting reactant by the mole ratio of product to reactant from the balanced equation gives the moles of product. Multiplying that by the product's molar mass converts it to a mass in grams. This assumes the reaction goes fully to completion with no losses.
Source:Chemistry (reaction stoichiometry)
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter moles of limiting reactant, mole ratio (product : reactant) and product molar mass.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Theoretical yield updates instantly as you type — no button to press.
Frequently asked questions
What is theoretical yield?
Theoretical yield is the maximum mass of product a reaction could form if it proceeded perfectly, with the limiting reactant completely converted and no losses. It is calculated from stoichiometry and serves as the benchmark for percent yield. Because real reactions never achieve it exactly, the actual yield is always less, and the two are compared to measure how efficient the reaction was.
What is a limiting reactant?
The limiting reactant is the reactant that is consumed first and therefore determines the maximum amount of product that can form. Once it runs out, the reaction stops, leaving any excess of the other reactants unused. Identifying the limiting reactant is the crucial first step in a theoretical yield calculation, since it alone sets the ceiling on product formation.
How do I find the mole ratio?
The mole ratio comes from the coefficients in the balanced chemical equation. If two moles of product form for every one mole of the limiting reactant, the ratio of product to reactant is two to one, so you enter 2. Always balance the equation first, then read the coefficients of the product and the limiting reactant to get the correct ratio.
Why convert moles to grams?
Reactions are governed by moles, but yields are usually weighed in grams in the lab, so converting makes the result practical. Multiplying the moles of product by its molar mass gives the theoretical mass you would collect if everything reacted perfectly. This calculator does the conversion, reporting both the product moles and the theoretical mass in grams for convenience.
How does theoretical yield relate to percent yield?
Theoretical yield is the denominator in the percent yield formula. After running a reaction and weighing the actual product, you divide the actual yield by the theoretical yield and multiply by 100 to get the percent yield. So calculating the theoretical yield accurately is essential for correctly judging how efficient your reaction turned out to be.