Percent Yield Calculator
Find the percent yield of a chemical reaction.
Results update as you type.
How it works
Percent yield measures how efficient a chemical reaction was by comparing the amount of product you actually obtained with the amount theory predicts you could obtain, and this calculator computes it in one step. You enter the actual yield, the mass of product recovered in the lab, and the theoretical yield, the maximum mass calculated from the balanced equation and the limiting reactant, and it returns the percent yield. Reactions rarely reach 100 percent because some reactant is lost to side reactions, remains unreacted, or is left behind during filtering, transferring, and purifying. A high percent yield indicates a clean, efficient process, while a low one prompts a chemist to investigate what went wrong or to accept the loss as inherent to the method. This metric is central to laboratory chemistry, industrial process design, and coursework, where it is a standard part of any synthesis write-up. It also helps compare methods: a route with a higher yield wastes less material and is usually cheaper. Both yields must be in the same unit, whether grams or moles, for the ratio to be valid. Enter the actual and theoretical yields to see the efficiency.
percent yield = actual yield / theoretical yield × 100
Percent yield compares how much product a reaction actually produced against the maximum it could produce in theory. Dividing the actual yield measured in the lab by the theoretical yield predicted from stoichiometry, then multiplying by 100, gives the percentage. A value near 100 percent means an efficient reaction with little loss, while a low value signals side reactions, incomplete conversion, or losses during purification.
Source:Chemistry (reaction stoichiometry)
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Worked example
How to use this calculator
- 1
Enter your values
Enter actual yield and theoretical yield.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Percent yield updates instantly as you type — no button to press.
Frequently asked questions
What is percent yield?
Percent yield is the ratio of the actual amount of product obtained from a reaction to the theoretical maximum, expressed as a percentage. It measures reaction efficiency. A percent yield of 90 means you recovered 90 percent of the product the balanced equation predicts. It accounts for real-world losses that always make actual results fall short of the ideal.
Why is percent yield rarely 100%?
Real reactions lose product for several reasons: competing side reactions form other substances, some reactant never reacts, the reaction may reach equilibrium before completing, and product is inevitably lost during filtering, transferring, and purifying. Impurities in reactants also reduce output. These unavoidable losses mean a perfect 100 percent yield is rare, and high yields are a mark of a well-designed procedure.
What is theoretical yield?
Theoretical yield is the maximum amount of product a reaction could produce if it proceeded perfectly and completely, calculated from the balanced chemical equation and the limiting reactant. It is the denominator in the percent yield formula. You find it by converting the limiting reactant to moles, applying the mole ratio to the product, and converting back to mass using the product's molar mass.
Can percent yield exceed 100%?
In principle no, but a calculated value above 100 percent can appear if the measured product is impure or still wet with solvent, making it weigh more than pure product would. It can also result from measurement or calculation errors. A yield over 100 percent is a red flag to dry and purify the product further and to recheck the theoretical yield calculation.
Do both yields need the same units?
Yes. The actual and theoretical yields must be expressed in the same unit, typically grams or moles, for the ratio to be meaningful. Mixing units, such as dividing grams by moles, would give a nonsensical result. This calculator assumes consistent units, so convert both figures to grams or both to moles before entering them.