This calculator finds the average of two or more percentages. Toggle "Allow different sample sizes" to switch from a simple average to a weighted average — essential when your percentages come from groups of unequal size.
How to Use This Calculator
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Enter the first percentage in Percent
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Enter the second percentage in Percent
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Click "Add more entries" to include up to 10 percentages.
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Check "Allow different sample sizes" if your percentages come from groups of different sizes, then enter each group size.
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Read the average percentage in the result panel.
How to Average Percentages
A percentage is a fraction with 100 in the denominator. Because percentages are numbers, you can average them exactly like any other set of numbers using the arithmetic mean formula.
Simple average works correctly when every percentage comes from a group of the same size. If 60% and 80% each describe groups of 50 people, the average is simply (60 + 80) ÷ 2 = 70%.
The trouble arises when the groups differ in size. A 60% result from 10 people and an 80% result from 1,000 people should not be averaged equally. The larger group carries more information and must be weighted accordingly.
Simple Average Formula
Use this formula when all percentages come from groups of the same size.
Average = (p1 + p2 + … + pn) ÷ n
Weighted Average Formula
Use this formula when groups differ in size. Each percentage is multiplied by its sample size before summing.
Weighted average = (p1 × n1 + p2 × n2 + … + pk × nk) ÷ (n1 + n2 + … + nk)
Simple vs. Weighted Average — When to Use Each
| Situation | Correct method |
|---|---|
| All groups have the same number of observations | Simple average |
| Groups differ in size | Weighted average |
| You only have the percentages and no group sizes | Simple average (assumption of equal groups) |
| Survey results from differently sized demographic groups | Weighted average |
| Student test scores where each student takes the same test | Simple average |
Example — Pancake Survey
A survey of 1,000 people asked whether they eat pancakes at least once a week. There were 300 teenagers, 450 adults aged 20–49, and 250 adults aged 50 and above. The results were 64%, 42%, and 36% respectively.
Simple (incorrect) average: (64 + 42 + 36) ÷ 3 = 47.33%
Weighted (correct) average: (64 × 300 + 42 × 450 + 36 × 250) ÷ (300 + 450 + 250) = (19,200 + 18,900 + 9,000) ÷ 1,000 = 47,100 ÷ 1,000 = 47.1%
The difference is small here, but it grows when group sizes are very unequal. Always use the weighted average when group sizes differ.
Pancake Survey Calculation
| Group | Percentage | Sample size | Weighted value | |||
|---|---|---|---|---|---|---|
| Teenagers | 64% | 300 | 64 × 300 = 19,200 | |||
| Adults 20–49 | 42% | 450 | 42 × 450 = 18,900 | |||
| Adults 50+ | 36% | 250 | 36 × 250 = 9,000 | |||
| Total | — | 1 | 000 | 47 | 100 ÷ 1 | 000 = 47.1% |
What Happens When All Sample Sizes Are Equal?
When every group is the same size, the weighted average equals the simple average. The weight cancels out:
Weighted average = (p1 × w + p2 × w + … + pn × w) ÷ (n × w) = (p1 + p2 + … + pn) ÷ n
This is why the "Allow different sample sizes" toggle is optional. If your groups are the same size, leave it off and use the simple average.
The average percentage calculator finds the mean of two or more percentages. When your percentages come from groups of different sizes, enable sample sizes to get a weighted average — the only statistically correct result.