Average Percentage Calculator
Paste two or more percentages to average them. If they come from groups of different sizes — quizzes with different question counts, samples of different sizes — add the sizes as weights to get the true combined percentage.
Example: with Percentages (comma or space separated) 72, 85, 91 · Weights or group sizes (optional, same order) → Average percentage: 82.67%.
Computed by the calculator below using its default values. Change any input to see your own numbers.
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When every percentage comes from the same-size group, averaging is simple: add them and divide by the count. Scores of 72%, 85%, and 91% average (72 + 85 + 91) ÷ 3 = 82.67%. That’s the calculation this tool runs when you leave the weights box empty.
When the groups differ in size, a plain mean misleads — you need a weighted average. Say you scored 90% on a 10-question quiz and 60% on a 30-question test. The simple mean says 75%, but you actually answered 9 + 18 = 27 of 40 questions correctly, which is 67.5%. Enter 90, 60 as the percentages and 10, 30 as the weights and the calculator computes (90×10 + 60×30) ÷ 40 for you. Use question counts, sample sizes, or dollar amounts as weights — whatever each percentage was measured against.
How it’s calculated
With no weights: average = (p₁ + p₂ + … + pₙ) ÷ n, the simple arithmetic mean. With weights: average = (p₁w₁ + p₂w₂ + … + pₙwₙ) ÷ (w₁ + w₂ + … + wₙ), the weighted mean, which equals the overall percentage of the combined group when the weights are the group sizes. Values parse from commas, spaces, semicolons, or line breaks; % signs are ignored. The weights list must match the percentage list in length, with a positive total.
Results update as you type and are estimates, not professional advice — verify important decisions with a qualified professional.
Common mistakes
- Averaging percentages from different-sized groups without weights — a 90% quiz and a 60% final are not worth the same.
- Adding percentages of different wholes together: 20% of the class plus 30% of the school is not 50% of anything.
- Averaging sequential percentage changes — +50% then −50% averages to 0% but actually leaves you down 25%; multiply the multipliers instead.
Frequently asked questions
How do I calculate the average of percentages?
If each percentage represents an equal-sized group, add them and divide by the count: 72%, 85%, and 91% average to 82.67%. If the groups differ, weight each percentage by its group size first.
When do I need a weighted average?
Whenever the percentages cover different amounts — test sections with different question counts, surveys with different sample sizes, returns on different account balances. Multiply each percentage by its size, add, then divide by the total size.
Can I just add percentages together?
Only when they are parts of the same whole, like budget shares of 40% + 35% + 25% = 100%. Percentages of different wholes must be converted back to raw numbers before combining.
Why is my weighted average different from the simple mean?
Because larger groups pull the answer toward their percentage. 90% of 10 questions and 60% of 30 questions gives 67.5% overall — closer to 60%, since the big test dominates.