Percent Yield Calculator
Enter the actual and theoretical yield of a reaction to get its percent yield, computed as actual divided by theoretical times 100. Use the 'Solve for' menu to work backward and recover the actual yield or the theoretical yield from a known percentage. A result above 100% is still shown but flagged, since it usually means the product is impure or not fully dried.
How to calculate percent yield
- Pick what to solve for in the 'Solve for' menu: percent yield, actual yield, or theoretical yield.
- Fill in the two known values; the visible fields change with your choice.
- Enter yields in grams and, when solving for a yield, the known percent in the 'Percent yield' field.
- Read the answer in the highlighted result box.
- Watch for the impurity warning if the percent yield lands above 100%, then use the Copy button.
Examples
Standard percent yield
Solve for percent yield, actual = 8 g, theoretical = 10 g
80%
Back out the theoretical yield
Solve for theoretical yield, actual = 8 g, percent = 80%
10
Yield above 100 percent
Solve for percent yield, actual = 11 g, theoretical = 10 g
110% (impurity warning shown)
Frequently asked questions
What is the percent yield formula?
Percent yield equals (actual yield / theoretical yield) x 100. The tool rounds to nine decimal places, so 8 g out of a possible 10 g gives exactly 80%.
How do I solve for actual or theoretical yield instead?
Rearrange the same relationship. Actual yield equals percent / 100 times theoretical, and theoretical yield equals actual divided by (percent / 100). The 'Solve for' menu does both for you.
What units should I use?
Any unit works as long as both yields share it. Grams is the default label, but moles, milligrams, or kilograms are fine because the units cancel in the ratio.
Can percent yield be over 100%?
Physically it should not exceed 100%. When it does, the tool still reports the number but shows an amber warning, because the usual cause is leftover solvent, water, or an impurity inflating the measured mass.
Why does the theoretical yield have to be more than zero?
The formula divides by the theoretical yield, and dividing by zero is undefined. The engine rejects a theoretical yield of zero or a negative value with an error rather than returning a meaningless result.
Can the actual yield be negative?
No. You cannot recover a negative mass of product, so a negative actual yield is rejected. Enter zero if the reaction produced nothing you could isolate.
How do I find the theoretical yield in the first place?
Balance the equation, identify the limiting reactant, use the mole ratio to find the maximum moles of product, then multiply by the product's molar mass to get grams.
Why is my percent yield low?
Common causes are competing side reactions, an incomplete or reversible reaction, product lost during filtration or transfer, and impure or wet starting material.
Is my data private?
Yes. Every calculation runs in your browser with no server round trip, so the numbers you enter never leave your device.
Learn more
- How to Find Theoretical Yield and Percent Yield
Work out theoretical yield from the limiting reactant, then turn a measured mass into a percent yield and read a result above 100 percent.
Related tools
Molar Mass Calculator
Calculate the molar mass and molecular weight of any chemical formula. Get a full per element breakdown for compounds like H2O, NaCl, H2SO4 and hydrates.
Molarity Calculator
Calculate molarity in mol per litre and solve for moles, volume or concentration. Find moles from mass and molar mass, then get the missing value.
Ideal Gas Law Calculator
Solve the ideal gas law PV = nRT for pressure, volume, moles or temperature. Enter any three values, pick your units in atm, kPa, L, m3, K or C.
555 Timer Calculator
Calculate 555 timer astable frequency, period, high and low times and duty cycle from R1, R2 and the timing capacitor. Free oscillator design helper.
Absolute Humidity Calculator
Calculate absolute humidity in grams of water vapor per cubic meter from air temperature and relative humidity. Fast, free and works in your browser.
Allele Frequency Calculator
Find allele frequencies from genotype counts. Enter the number of AA, Aa and aa individuals to get the A and a allele frequencies and allele totals.