📊 Percent Yield Calculator
Compare what you made with what the reaction predicted. Enter actual and theoretical yields in grams or moles — or build the theoretical from expected moles and molar mass — for the percent yield.
📊 Percent yield
Good yield for a typical synthesis.
Percent yield = (actual ÷ theoretical) × 100, with both in the same units. For educational use — verify against authoritative sources and follow proper lab safety.
How efficient was the reaction?
Percent yield measures how much of the theoretical maximum a reaction actually delivered. It rewards clean chemistry and careful technique, and a suspiciously high value (over 100 %) is a red flag for impurity or error rather than a triumph.
Get the theoretical mass by turning moles into grams with the Molar Mass Calculator, and use the Molarity Calculator when your reagents are solutions rather than solids.
❓ Frequently Asked Questions
How is percent yield calculated?
Percent yield = (actual yield ÷ theoretical yield) × 100, with both yields in the same units (grams or moles). The actual yield is what you actually recovered; the theoretical yield is the maximum the balanced equation predicts from the limiting reagent. Recovering 8 g when 10 g is possible is an 80 % yield.
How do I find the theoretical yield?
From stoichiometry: find the moles of limiting reagent, apply the mole ratio from the balanced equation to get moles of product, then convert to grams with the product's molar mass (theoretical grams = moles × molar mass). This tool's 'Moles × molar mass' mode does that last step for you — for example 0.5 mol of glucose (180.156 g/mol) is a 90.078 g theoretical yield.
Can I work in moles instead of grams?
Yes. Percent yield is a ratio, so as long as the actual and theoretical figures are both in moles (or both in grams), the percentage is the same. Switch the units selector to moles and enter the actual and theoretical amounts directly.
What does a yield over 100 % mean?
It is physically impossible for the pure product, so it signals a problem rather than a great reaction. The usual causes are an impure product (residual solvent, water, or unreacted starting material still weighed in), a sample that wasn't fully dried, or a weighing/measurement error. Dry and purify the product and re-weigh before trusting the number.
Why is my yield well below 100 %?
Real reactions lose product to competing side reactions, incomplete conversion, and losses during workup, transfer, filtration, and purification. Many good preparations land in the 70–90 % range. This tool is for educational use — verify against authoritative sources and follow proper lab safety.