What is theoretical yield?

Theoretical yield is the maximum product obtainable if the reaction goes to completion with no losses. It equals moles of limiting reagent × the product-to-reagent mole ratio × the product's molar mass, expressed in grams.

How is percent yield calculated?

Percent yield = actual yield ÷ theoretical yield × 100. If you isolate 8.2 g of a product whose theoretical yield is 10.0 g, the percent yield is 82 percent. It measures how efficiently the reaction and workup converted reagent to isolated product.

What is the limiting reagent?

The limiting reagent is the reactant that runs out first and therefore caps how much product can form. All yield calculations are based on it. If you are unsure which reagent is limiting, compute the product each reagent could give and pick the smallest.

Can percent yield exceed 100 percent?

Not legitimately. A value above 100 percent usually means the isolated product is impure or still wet with solvent, the molar masses are wrong, or the stoichiometry is mis-entered. Re-check purity and your inputs before reporting it.

What is the stoichiometric ratio I enter?

It is the moles of product formed per mole of limiting reagent, taken from the balanced equation. For A → B it is 1. For a reaction producing 2 moles of product per mole of limiting reagent it is 2; for one producing half a mole, it is 0.5.

Chemical Reaction Theoretical & Percent Yield Calculator

Every synthesis is judged on yield, and yield only means something when it is referenced to the theoretical maximum set by the limiting reagent. This calculator computes theoretical yield from stoichiometry and then your percent yield from what you actually isolated.

How it works

Theoretical yield flows from the moles of limiting reagent through the balanced equation to the product mass:

moles_limiting   = mass_limiting / molar_mass_limiting   (if entered by mass)
moles_product    = moles_limiting × ratio                (ratio from equation)
theoretical (g)  = moles_product × molar_mass_product
percent yield    = actual_yield / theoretical × 100

The ratio is the moles of product per mole of limiting reagent read straight off the balanced equation. If you already know moles of limiting reagent, you can enter them directly and skip the mass and molar-mass step.

Example and tips

Reacting 0.10 mol of a limiting reagent in a 1:1 reaction to a product of molar mass 180 g/mol gives a theoretical yield of 18.0 g. Isolating 14.4 g is an 80% yield. A percent yield above 100% is a red flag for an impure or solvent-wet product, a wrong molar mass, or a stoichiometry slip — re-check before reporting. Confirm which reactant is actually limiting first; basing the calculation on a reagent in excess overstates the theoretical yield and understates your true efficiency.