This theoretical yield calculator computes the maximum product a reaction can make: reactant mass → moles → mole ratio → product moles → product mass, with optional percent yield when you enter what you actually got.
| Moles of reactant | – |
| Theoretical yield | – |
| Percent yield (if actual given) | – |
The Ceiling Every Real Yield Is Measured Against
Given an actual result, the score against this ceiling is our Percent Yield Calculator; full reaction bookkeeping lives in the Stoichiometry Calculator. Part of our Chemistry Calculators collection.
Worked Example (Verified)
- Decomposing 10 g CaCO₃ → CaO + CO₂ (defaults): 10/100.09 = 0.0999 mol CaCO₃ → ×(1/1) × 56.08 = 5.60 g CaO theoretical · an actual 5.0 g = 89.2% yield
- The ratio does the chemistry: for 2 H₂ + O₂ → 2 H₂O, 8 g O₂ (0.25 mol) with coefficients 1 → 2 makes 0.5 mol H₂O = 9.0 g — enter cr 1, cp 2 to see coefficients earn their keep
- Theoretical yield assumes the named reactant fully converts and is limiting — if another reactant runs out first, it, not this one, sets the ceiling (limiting-reagent analysis)
Yield Discipline
- Balance the equation before touching coefficients — every wrong coefficient is a wrong answer with confidence.
- Use the limiting reactant’s amount; excess reactants contribute nothing beyond their partner’s supply.
- Yields above 100% mean wet product, impurities or a weighing error — chemistry doesn’t give change back.
- Atom economy ≠ yield: a 100% yield of a reaction that wastes half its atoms as byproduct is perfect execution of an inefficient design.
Related Tools
- Percent Yield Calculator — actual vs theoretical
- Stoichiometry Calculator — reaction bookkeeping
- Chemistry Calculators — the full collection
Frequently Asked Questions
How do you calculate theoretical yield?
Convert reactant grams to moles (÷ molar mass), multiply by the product:reactant coefficient ratio from the balanced equation, then convert product moles back to grams (× product molar mass). Example: 10 g CaCO₃ (0.0999 mol) → 0.0999 mol CaO → 5.60 g. This calculator runs the three steps with your coefficients.
What is the difference between theoretical and percent yield?
Theoretical yield is the maximum possible product mass (grams) from stoichiometry. Percent yield compares reality to it: actual ÷ theoretical × 100. The theoretical yield calculator here optionally reports both when you add an actual mass.
Why is actual yield always lower?
Side reactions, incomplete conversion, equilibrium limits, product lost in transfers/filtration/drying, and side products. Industrial yields of 80–95% are good; multi-step syntheses multiply step yields (0.9⁵ ≈ 59%) — the tyranny of the product of fractions.
Which reactant do I use for theoretical yield?
The limiting one — the reactant that exhausts first at the equation’s ratios. If you’re given amounts of several, compute the product each could make and take the smallest; that reactant’s row is the one to enter here.
Can theoretical yield be in moles instead of grams?
Yes — the mole step (here 0.0999 mol) IS the theoretical yield in moles; the final × molar mass merely dresses it in grams. Gas products are often reported in litres at STP instead (moles × 22.4 L).
Is this theoretical yield calculator free?
Yes — free, instant, no sign-up.