Actual Yield Calculator

Almost no reaction hands you everything stoichiometry promises. Side reactions eat into the product, transfers leave material on the glassware, and the last filtrate always keeps a little for itself. Actual yield is what you weigh at the end. Percent yield is how much of the textbook maximum you actually walked away with.

What actual yield really measures

Actual yield is the mass of pure product you end up with after a reaction, weighed on a balance. Theoretical yield is the upper bound: the amount you would get if every molecule of the limiting reagent converted cleanly and you recovered all of it. The gap between the two tells you something about both the reaction and your bench technique. A clean product close to the theoretical number means the chemistry cooperated and your hands were steady. A big gap usually points at a sluggish equilibrium, a competing side reaction, or material lost during workup.

How to use it

Type in any two of the three numbers and read off the third. Know the theoretical yield from your balanced equation and the actual yield from your weighing? You will get the percent yield. Have a target percent yield for a reaction you have not run yet? Put in the theoretical yield and the target percent, and the actual yield prediction fills in. If the percent yield comes back above 150 percent you will see a warning. That is almost always wet product, residual solvent, or starting material crashing the party rather than a miracle reaction.

Reading the percent yield

\frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100 = \text{\% Yield}

Divide actual by theoretical, multiply by 100, and you have a percent yield. Most decent reactions land somewhere between 50 and 90 percent. Under 100 is normal: you lost material somewhere, or the equilibrium never finished, or a competing reaction stole some of your starting material. Over 100 is more interesting. It usually means your product brought passengers: solvent that did not evaporate, water pulled from the air, unreacted starting material co-crystallizing in the flask. Anything above about 150 percent is almost certainly a weighing problem or a sample that needs another wash and a longer time in the vacuum oven.

Tips for trustworthy numbers

Dry the product fully before you weigh it. Residual solvent or atmospheric water shows up as percent yield you did not actually earn.
Match the balance to the scale of the reaction. Four decimal places (0.0001 g) for milligram work; three is fine for gram scale. Pushing past that adds noise, not information.
Confirm purity with NMR, IR, or a melting point before you commit to the number. A high yield of an impure mix is not a high yield.
Budget for losses on transfers, filtration, and recrystallization. A literature procedure that reports 92 percent often becomes 70 in someone else's hands the first time around.

FAQ

Can percent yield go above 100 percent?

It can, and when it does it usually means your sample is not as pure as you would like. Residual solvent, unreacted starting material, or absorbed water all add mass without adding actual product. If you are consistently over 100, run another wash, dry it longer, or re-check the molar mass and stoichiometry in your theoretical-yield calculation.

What counts as a good percent yield?

It depends on what you are running. A well-tuned single-step reaction often lands between 70 and 90 percent; a clean, straightforward transformation can push past 90. Multi-step syntheses are punishing: even a respectable 80 percent per step compounds down to roughly 40 percent after four steps. Workup choices, scale, and how aggressive the purification is all move the number around.

Why is my actual yield higher than my theoretical yield?

Your product is heavier than the pure compound. Most often the culprit is wet solvent, inorganic salts from an incomplete wash, or a co-crystallized impurity. Re-purify, dry the sample to constant weight, and weigh again before trusting a yield over 100 percent.