Percent Yield Calculator
Actual over theoretical, and what a figure above 100 means.
Work out Percent Yield. Actual over theoretical, and what a figure above 100 means. Says which constants are exact and which are conventions.
Percent yield
85.000%
good · 1.5 g unaccounted for
Percent yield is actual over theoretical. Losses come from incomplete reaction, competing side reactions, and simple mechanical transfer — product left on the filter paper and the glassware. Above 90% is excellent for most preparations, and synthetic routes with many steps compound their losses multiplicatively: five steps at 80% each leaves 33%.
How the Percent Yield Calculator works
Percent yield is actual over theoretical. Losses come from incomplete reaction, competing side reactions and simple mechanical transfer — product left on the filter paper and the glassware. A figure above 100% means something is wrong, not that something went well.
Also known as: percentage yield formula · theoretical yield calculator · reaction yield calculator · how to calculate percent yield
Frequently asked questions
How do I calculate percent yield?
Divide the actual yield by the theoretical yield and multiply by 100. Getting 8.5 g where 10 g was possible is 85%.
What does a yield above 100% mean?
An error, almost always. The product is usually still wet with solvent or contaminated with unreacted starting material. Dry to constant mass and weigh again.
What is a good percent yield?
Above 90% is excellent for a simple preparation, 70–90% is good, and below 40% suggests something worth investigating. Context matters — some reactions are inherently low-yielding.
Why do multi-step syntheses lose so much?
Because yields multiply rather than average. Five consecutive steps at 80% each leave 33% of what you started with, which is why route design favours fewer steps.
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