BYTETOOLS

Percent Yield Calculator

Calculate percent yield from actual and theoretical yield, or solve for either one. Includes a grams-to-moles helper and an explanation of yields over 100%.

82.00%
Percent yield
8.2
Actual (g)
10
Theoretical (g)
1.8
Shortfall (g)

Good yield

% yield = (actual ÷ theoretical) × 100

What is the Percent Yield Calculator?

Percent yield compares what a reaction actually produced with the maximum the stoichiometry allows: percent yield = (actual ÷ theoretical) × 100. Isolating 8.2 g when 10 g was possible is an 82% yield.

  • Solves for percent yield, actual yield or theoretical yield
  • Works in grams or moles
  • Optional formula parser for the product's molar mass
  • Visual bar and plain-English rating of the yield
  • Explains what a yield above 100% really means
  • Entirely browser-based — nothing is uploaded

How to use the Percent Yield Calculator

  1. 1

    Choose whether to solve for percent yield, actual yield or theoretical yield.

  2. 2

    Pick whether your yields are in grams or moles.

  3. 3

    Enter the two values you know.

  4. 4

    Optionally type the product formula to see the other unit as well.

  5. 5

    Read the percent yield and copy the summary.

About the Percent Yield Calculator

The ByteTools Percent Yield Calculator works out how efficient a reaction was. Enter the mass or moles you actually isolated together with the theoretical yield from your stoichiometry, and it returns the percent yield, the shortfall and a plain-English rating of the result.

The same tool runs backwards. If you know the percent yield your method usually gives, it will tell you how much product to expect; if you know how much you got and what fraction that represents, it recovers the theoretical yield. An optional formula box converts between grams and moles using the product's molar mass.

All the calculations happen in your browser with JavaScript and nothing is sent anywhere. That makes it quick to check a lab write-up on a phone, and the page carries on working without an internet connection.

Frequently asked questions

How do you calculate percent yield?

Divide the actual yield by the theoretical yield and multiply by 100. If a reaction that could give 10 g of product actually gave 8.2 g, the percent yield is (8.2 ÷ 10) × 100 = 82%.

What is theoretical yield?

It is the maximum mass of product the balanced equation allows from the limiting reagent, assuming the reaction goes to completion with no losses. You calculate it by converting the limiting reagent to moles, applying the mole ratio, then converting back to grams.

Can percent yield be more than 100%?

Not genuinely. A figure above 100% almost always means the product is still wet with solvent, or that an impurity or unreacted starting material was weighed with it. Dry the sample to constant mass and weigh again before recording the result.

What counts as a good percent yield?

It depends heavily on the chemistry. Above 90% is excellent for a simple one-step reaction, 70–90% is a good result for most preparations, and multi-step syntheses often accept far lower figures because losses compound at every stage.

Why is my percent yield so low?

Common causes are an incomplete reaction, a competing side reaction, product lost during filtration or transfer, and losses in recrystallisation. Reversible reactions that reach equilibrium can never reach 100% conversion in a single pass.

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