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Average Percentage Calculator

Calculate average percentage online — free, step by step. Simple mean of two percentages, or the correct weighted average from parts and wholes.

Quick answer
How do you average percentages?
If the percentages come from equally sized groups, the average is their simple mean: (p₁ + p₂) ÷ 2. If the groups differ in size, you must weight: sum all parts and all wholes separately, then divide — (part₁ + part₂) ÷ (whole₁ + whole₂) · 100. The simple mean is otherwise wrong.
The tool

Enter values — get full working

Average of two percentages.
Comma or dot as decimal separator, negative values allowed.
Step-by-step
Press Calculate to see every step.
HowTo

Average Percentage Calculator — step-by-step

How do you average percentages?
  1. 1
    Step 1 of 4

    Check whether the groups are equal in size

    Equal groups → simple mean. Different sizes → weighted average.

  2. 2
    Step 2 of 4

    Simple mean

    Add both percentages and divide by 2: (40% + 60%) ÷ 2 = 50%.

  3. 3
    Step 3 of 4

    Weighted: sum parts and wholes

    Add all hits and all totals separately. Example: (20 + 30) hits out of (50 + 150) = 50 out of 200.

  4. 4
    Step 4 of 4

    Weighted: divide and times 100

    50 ÷ 200 · 100 = 25%. That is the correct overall percentage.

Examples

Average Percentage Calculator — examples

Worked examples with full working
avg(40%, 60%)
(40 + 60) ÷ 2
50%
20/50 + 30/150
(20 + 30) ÷ (50 + 150) · 100
= 50 ÷ 200 · 100
25%
avg(80%, 90%)
(80 + 90) ÷ 2
85%
9/10 + 1/90
(9 + 1) ÷ (10 + 90) · 100
10%
avg(33%, 67%)
(33 + 67) ÷ 2
50%
45/50 + 5/50
(45 + 5) ÷ (50 + 50) · 100
50%
Theory

How do you average percentages correctly?

You may only average percentages directly when they refer to equally sized populations. Otherwise the simple mean distorts the result, because it weights small and large groups equally. The correct approach is the weighted average: sum the parts (e.g. the hits) and the wholes (each group size) separately, then divide. Formula: (part₁ + part₂ + …) ÷ (whole₁ + whole₂ + …) · 100. Example: 90% of 10 items and 1% of 90 items together give only 10% — not 45.5%. This is one of the most common mistakes in statistics and grade calculation.

Pitfalls

Common mistakes

Simple mean for unequal groups

For different group sizes, (p₁ + p₂) ÷ 2 is wrong — weight instead.

Adding percentages directly

Percentages from different bases can't simply be summed.

Forgetting the weights

The weights are the group sizes (the wholes), not the percentages.
FAQ

Frequently asked questions

Glossary

Glossary — key terms explained simply

Whole (base)
The reference value that equals 100%.
Part (value)
The amount that belongs to a percentage.
Rate
The percentage (per hundred).
Difference
The result of a subtraction (new − old).
Relative
Expressed against a reference, dimensionless.
Absolute
In the unit of the quantity, without reference.
Factor
Number you multiply by (e.g. 1.25 for +25%).
Percentage point
Absolute difference between two percentages.