Theoretical Yield Calculator (grams)
Find the theoretical yield in grams from the moles of limiting reagent, the mole ratio and the product molar mass.
How it works
moles of product = moles of limiting reagent × mole ratio · theoretical yield (g) = moles of product × molar mass
Theoretical yield is the maximum mass of product a reaction can make if it goes to completion with no losses. Multiply the moles of the limiting reagent by the product-to-reagent mole ratio from the balanced equation to get moles of product, then multiply by the product's molar mass to reach grams. The real (actual) yield is usually lower, and percent yield compares the two.
Worked example
Burning 2 mol of H₂ to make water (2 H₂ + O₂ → 2 H₂O, a 1:1 ratio of H₂ to H₂O) gives 2 mol of H₂O; at 18.015 g/mol that is a theoretical yield of 2 × 18.015 = 36.03 g.
Sources: Yield (chemistry) — Wikipedia
Frequently asked questions
Where does the mole ratio come from?
From the coefficients of the balanced equation: divide the product coefficient by the limiting-reagent coefficient. For 2 H₂ + O₂ → 2 H₂O the H₂-to-H₂O ratio is 2:2, i.e. 1.
How do I get moles of limiting reagent from grams?
Divide the reagent mass by its molar mass. If you have two reactants, first work out which one runs out first — that is the limiting reagent.
Why is the actual yield lower?
Side reactions, incomplete conversion, losses during transfer and purification, and impurities all reduce the mass you actually recover below the theoretical maximum.
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Educational estimate. Check the formula, units and significant figures for your exact case.