About the Percent Yield Calculator
Percent Yield Calculator tells you how well a chemical reaction worked. Percent yield is the actual yield, the mass of product you really collected, divided by the theoretical yield, the most the reaction could make, times 100. If you already know both masses, enter them. If you only know the mass of the limiting reactant, enter it with the molar masses and the coefficients from the balanced equation and the page works out the theoretical yield first. The answer is shown with the amount lost or not formed, and a warning if it is above 100%.
Updated October 2026
How to use the Percent Yield Calculator
- 1Choose whether you know the theoretical yield or the limiting reactant.
- 2Enter the actual yield in grams.
- 3Enter the theoretical yield, or the reactant mass, molar masses and coefficients.
- 4Read the percent yield.
- 5Copy the result for your lab report.
Why yield matters
Chemists, students and manufacturers all ask how much of the possible product they got. A low yield wastes expensive reagents, so a process is judged by its yield as well as its purity. In a teaching lab, the percent yield is also a check on technique: it shows how much was lost in handling.
Working out the theoretical yield
Take 10 g of HCl in the reaction NaOH + HCl → NaCl + H2O, where HCl (36.46 g/mol) and NaCl (58.44 g/mol) are in a 1 to 1 ratio. That is 0.274 mol of HCl, which could make 0.274 mol of NaCl, or 16.0 g. If you collected 14.4 g, the percent yield is 90%.
- grams of reactant ÷ molar mass = moles of reactant
- moles of reactant × (product coefficient ÷ reactant coefficient) = moles of product
- moles of product × molar mass = theoretical grams
Improving your result
Weigh carefully, rinse equipment into the product, dry the product completely and avoid transferring between containers more than you need. If your yield is over 100%, dry the product longer and weigh again.
Related tools
Balance the equation first with the Chemical Equation Balancer, find molar masses with the Molecular Weight Calculator and convert amounts with the Mole Calculator. The Percent Error Calculator measures accuracy in other experiments.
Features
- Direct percent yield
- Theoretical yield from the limiting reactant
- Mole ratio from the balanced equation
- Shows the amount lost
- Warns about yields above 100%
- Private: nothing is uploaded
Frequently asked questions
What is percent yield?
The percentage of the maximum possible product that you actually obtained: percent yield = actual yield ÷ theoretical yield × 100.
What is the theoretical yield?
The mass of product the reaction would make if everything reacted perfectly, calculated from the amount of the limiting reactant.
Why is the yield below 100%?
Reactions may be incomplete, produce side products, or lose material during filtering, transfer and drying.
Can a yield be above 100%?
Not in theory. In practice a result over 100% usually means the product is wet or impure, or a measurement is wrong.
How do I find the theoretical yield?
Convert the limiting reactant to moles, multiply by the mole ratio product to reactant from the balanced equation, and convert the moles of product to grams.
What is a good percent yield?
It depends on the reaction. Simple reactions can give over 90%, while multi-step syntheses often give much less.
How do I know which reactant is limiting?
The one that would produce the least product. Work out the product from each reactant and take the smaller.
What if my reaction has more than one product?
Pick the product you are measuring. Each product has its own theoretical yield, found with its own molar mass and coefficient.
Is percent yield the same as percent purity?
No. Yield compares the amount obtained with the amount expected. Purity says how much of what you obtained is the wanted substance, and a low purity can hide a real yield that is lower than it looks.
Is my data stored?
No. It is calculated in your browser.