What percent yield tells you
Percent yield = (actual ÷ theoretical) × 100. The theoretical yield is what a perfect reaction would produce (from stoichiometry, assuming 100% conversion and zero losses); the actual yield is what your lab bench produced. Real yields are always below 100% — losses come from incomplete reactions, side products, transfer spills and purification steps.
Interpreting your number
- 90–100% — excellent; typical for simple precipitations and distillations.
- 70–90% — normal for most organic syntheses.
- 50–70% — common for multi-step or air-sensitive reactions; not a failure.
- <50% — something went sideways: check for spilled product, incomplete drying, wrong limiting reagent.
- Over 100% — your product is wet or impure. Weigh again after proper drying; ">100% yield" is a purity problem, not a miracle.
Reverse mode
Set a target percent (e.g. 85%) and leave actual or theoretical empty — the calculator fills the missing value. Useful for planning: "if I want 85% of the 4.0 g theoretical, how much should I recover?" (answer: 3.4 g).
Units must match (both grams or both moles). The calculator doesn't do stoichiometry itself — use the Stoichiometry Calculator to find theoretical yield from a balanced equation first.