Percent Yield Calculator

Frequently Asked Questions

How do I calculate percent yield?

Percent yield is the actual yield divided by the theoretical yield, multiplied by one hundred. Both yields must be in the same units.

Why is my percent yield above 100 percent?

A yield above one hundred percent usually means the product is impure or wet, or there was a weighing error. A real reaction cannot produce more than the theoretical maximum.

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Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How This Calculator Works

Percent yield measures how efficient a reaction was by comparing how much product you actually recovered with the maximum amount predicted by stoichiometry. It equals the actual yield divided by the theoretical yield, multiplied by one hundred. A value below one hundred percent reflects losses from incomplete reactions, side reactions, or product lost during transfer and purification.

Both yields must be in the same units, whether grams or moles, so the ratio is dimensionless.

How To Use It

Enter the actual yield you measured in the lab and the theoretical yield calculated from the limiting reagent. The result is the percent yield. A figure above one hundred percent usually signals impurities or a weighing error rather than a real surplus.

Where It Applies

Evaluating laboratory synthesis efficiency.

Comparing reaction routes in process chemistry.

Flagging contamination when results exceed one hundred percent.

Common Sources of Yield Loss

A theoretical yield of 100% is never achieved in practice. The gap between theoretical and actual yield comes from several sources: side reactions divert reactants into unwanted products; reversible reactions reach equilibrium before completion; product is lost during filtration, transfer, or purification steps; and mechanical losses occur during crystallization or distillation. Even in highly optimized industrial processes, yields of 85–95% are considered excellent.

In multistep synthesis, yield losses multiply. A five-step synthesis with 90% yield at each step gives an overall yield of only 0.9⁵ = 59%. This compounding effect is why synthetic chemists spend considerable effort optimizing each step and why reducing step count is often the most effective route to improving overall yield. Green chemistry metrics such as atom economy and E-factor complement percent yield by measuring how much of the starting material ends up in the product versus waste.

Frequently Asked Questions

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