What is percent yield?

Percent yield is the ratio of the actual yield (what you actually collected) to the theoretical yield (the maximum possible based on stoichiometry), multiplied by 100. Formula: % Yield = (Actual Yield / Theoretical Yield) × 100.

Can percent yield exceed 100%?

Theoretically no — 100% is the maximum. A value above 100% usually means the product is contaminated with impurities (solvent, unreacted reagents), the product was not fully dried, or there was a measurement error. It does not violate conservation of mass for pure product.

What units should I use?

Actual yield and theoretical yield must be in the same unit (both in grams, both in moles, etc.) for the ratio to be dimensionless. This calculator supports grams (g), moles (mol), and millimoles (mmol) as a label — the math is identical regardless of unit as long as both values share the same one.

How do I find the theoretical yield?

Theoretical yield comes from stoichiometry: identify the limiting reagent, use molar ratios from the balanced equation, and multiply by the molar mass of the product to convert moles to grams. Once you have the theoretical yield, plug it into this calculator.

What is a good percent yield?

It depends on the reaction. In undergraduate labs 70–90% is typical. Industrial processes often aim for 95%+. Complex multi-step syntheses may give 40–60% per step. A yield below 40% usually signals a problem worth investigating.

Percent Yield Calculator

Name: Percent Yield Calculator
Availability: InStock
Author: Nham Vu

Enter the actual and theoretical yield of your reaction to instantly calculate percent yield — or solve for any missing variable.