Reaction Yield Calculator
The Gap Between What Should Happen and What Does
No reaction in a real flask converts every last molecule of reactant into product — side reactions, incomplete conversion, and losses during purification all take a share. Percent yield is how chemists quantify exactly how much of that theoretical maximum was actually captured, and it's one of the first numbers reported in any synthesis writeup.
The Formula
Theoretical yield is the maximum amount of product possible, calculated from the limiting reactant using stoichiometry. Actual yield is what was actually isolated and weighed at the end of the experiment.
Where This Calculation Matters
- Evaluating a synthesis — percent yield is the standard metric for judging how efficiently a reaction ran.
- Process scale-up — manufacturers track yield closely, since even small percentage drops become expensive at industrial scale.
- Troubleshooting a procedure — an unexpectedly low yield often points to a side reaction, incomplete reaction, or product lost during workup.
- Comparing reaction conditions — yield is the metric used to judge whether a change in temperature, catalyst, or solvent actually improved a reaction.
Worked Examples
| Actual Yield | Theoretical Yield | Percent Yield |
|---|---|---|
| 8.5 g | 10.0 g | 85.0% |
| 45 g | 50 g | 90.0% |
| 3.2 g | 4.0 g | 80.0% |
Yields above roughly 90% are considered excellent for most organic syntheses; multistep sequences often compound lower yields at each step into a much lower overall yield.
How to Use This Calculator
- Enter the Actual Yield (g) — the mass of product actually obtained.
- Enter the Theoretical Yield (g) — the maximum possible mass calculated from stoichiometry.
- Select Calculate to get the percent yield.
Related Calculations
Need the theoretical yield itself first? The Stoichiometry Calculator computes product mass from a balanced equation. If more than one reactant is involved, check the Limiting Reactant Calculator to confirm which one caps the theoretical yield.