Percent Yield Calculator

How It Works

Enter the actual yield (the mass of product you collected in your experiment) and the theoretical yield (the maximum possible mass calculated from stoichiometry). The calculator divides actual by theoretical and multiplies by 100 to express reaction efficiency as a percentage. A progress bar visualizes your yield relative to 100%.

Formula

Worked Examples

• Actual 4.5 g, Theoretical 5.0 g → % yield = 90%
• Actual 2.8 g, Theoretical 4.0 g → % yield = 70%
• Actual 18.2 g, Theoretical 20.0 g → % yield = 91%

What Affects Percent Yield?

The most common causes of yield below 100% include: incomplete reactions (many reactions reach an equilibrium before all limiting reagent is consumed), competing side reactions that divert reactants toward undesired products, mechanical losses during product isolation (filtration, crystallization, solvent evaporation, column chromatography), solubility of the product in the reaction solvent, and human measurement error. Improving technique — accurate weighing, careful transfer, optimized reaction conditions — typically raises percent yield over time.

Percent Yield in Industry vs. the Lab

In undergraduate labs, a 70–90% yield is considered successful. In pharmaceutical synthesis, even a 50% yield per step is sometimes acceptable for complex molecules, but a 10-step synthesis at 90% yield per step gives only 35% overall. Industrial processes are optimized relentlessly because even a 1% improvement in yield across millions of kilograms of product translates to enormous cost and waste reduction. Atom economy — a related concept — measures what fraction of all atoms in reactants end up in the desired product.

Using Percent Yield to Diagnose Lab Technique

Consistently low percent yield on the same reaction is a signal worth investigating. Track actual yields over multiple attempts and compare conditions: temperature, reaction time, solvent, workup procedure. A sudden drop in yield often indicates contaminated reagents, incorrect molarity of a solution, or a step change in technique.

Frequently Asked Questions

What is percent yield?

Percent yield measures the efficiency of a chemical reaction — how much product you actually obtained versus the theoretical maximum. A 100% yield would mean no product was lost at any step, which is rarely achieved in practice.

Can percent yield exceed 100%?

Percent yield should not exceed 100%. If it appears to, the most likely explanations are: the product is impure and retains solvent or water (inflating the measured mass), or the theoretical yield was calculated incorrectly. If you see >100%, check both your calculation and the purity of your product.

What is a good percent yield?

In academic labs, 70–90% is considered good for most reactions. A yield above 90% is excellent. Industrial processes vary widely — some commodity chemicals achieve 99%+ yield, while complex syntheses may target 60–80% per step.

How do I calculate theoretical yield?

Theoretical yield requires: identifying the limiting reagent, applying the stoichiometric mole ratio to find moles of product, then multiplying by the product's molar mass. Use the Theoretical Yield Calculator for a guided workflow.

What is the difference between percent yield and atom economy?

Percent yield measures how much of the theoretical maximum you recovered in a specific experiment. Atom economy measures how much of the combined mass of all reactants ends up in the desired product — a property of the reaction itself, independent of experimental technique. High atom economy reactions produce fewer waste byproducts.