Percent Yield Calculator
Calculate the percent yield of a chemical reaction by comparing the actual yield (what you recovered in the lab) to the theoretical yield (what stoichiometry predicts). Get an instant efficiency rating, step-by-step explanation, and visual breakdown.
What Is Percent Yield?
Percent yield is a measure of reaction efficiency in chemistry. It compares the actual yield (the amount of product you actually obtained from a reaction) to the theoretical yield (the maximum amount of product that could be obtained based on stoichiometric calculations).
The Formula
Percent Yield = (Actual Yield ÷ Theoretical Yield) × 100%
Actual yield is what you recovered in the lab.
Theoretical yield is what stoichiometry predicts.
What the Results Mean
- 90–100%: Excellent — highly efficient reaction, minimal loss
- 70–89%: Good — typical for many organic reactions
- 50–69%: Fair — acceptable but room for improvement
- Below 50%: Poor — significant product loss; check procedure
- Above 100%: Impossible in theory — indicates impurities or measurement error
Common Reasons for Low Percent Yield
- Incomplete Reactions: Reaction did not go to completion.
- Side Reactions: Unwanted reactions consumed reactants.
- Product Loss: Loss during transfer, filtration, or purification.
- Impure Reactants: Starting materials contained impurities.
- Measurement Errors: Inaccurate weighing or volume measurement.
Why Use This Percent Yield Calculator?
- Instant Results: Get percent yield and efficiency rating immediately.
- Step-by-Step Breakdown: See exactly how the calculation works.
- Visual Comparison: Bar charts show actual vs. theoretical yield.
- Multiple Units: Works with grams, moles, milligrams, or kilograms.
- Free & Private: No registration, no data storage.
❓ Percent Yield Calculator FAQ
What is percent yield?
Percent yield is the ratio of the actual yield to the theoretical yield, expressed as a percentage. It measures the efficiency of a chemical reaction.
How is percent yield calculated?
Percent yield = (Actual Yield ÷ Theoretical Yield) × 100%. For example, if you recovered 1.6 g of product and the theoretical yield is 2.0 g, the percent yield is 80%.
What is the difference between actual yield and theoretical yield?
Actual yield is the amount of product you actually obtain from a reaction in the lab. Theoretical yield is the maximum amount of product that could be obtained based on stoichiometric calculations, assuming 100% efficiency.
Can percent yield be over 100%?
In theory, no — percent yield cannot exceed 100% because the actual yield cannot exceed the theoretical yield. If you get a result over 100%, it usually indicates impurities in your product or measurement errors.
What is a good percent yield?
A "good" percent yield depends on the reaction type. In undergraduate organic chemistry labs, yields of 50-90% are common. Industrial processes often achieve 90%+ yields.
What causes low percent yield?
Low percent yield can result from incomplete reactions, side reactions, product loss during transfer or purification, impure reactants, or measurement errors.
What units does this calculator support?
This calculator supports grams (g), moles (mol), milligrams (mg), and kilograms (kg). Both actual yield and theoretical yield must use the same unit.
How do I find the theoretical yield?
The theoretical yield is calculated from the balanced chemical equation using stoichiometry. You start with the limiting reactant, convert to moles, use the mole ratio from the balanced equation, then convert to grams of product.
What is the difference between percent yield and percent recovery?
Percent yield compares actual yield to theoretical yield from a reaction. Percent recovery compares the amount of a substance recovered after purification to the amount you started with.
Is this calculator free?
Yes, this calculator is completely free to use. No registration or personal data storage is required. All calculations are performed in your browser.