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Average Percentage Calculator

Average a list of percentages in one step — and see the weighted average alongside it. Averaging percentages from differently-sized groups is one of the most common statistical mistakes there is, so this calculator shows both numbers rather than letting you pick the wrong one by accident.

What is the average of these percentages?

Separate each one with a comma.

Optional. Add the size behind each percentage to get the weighted average.

Enter your numbers and press Calculate — the full working appears here.

The averaging trap

Suppose you score 80% on a 10-mark quiz and 60% on a 90-mark exam. The plain average says 70%. Your actual result:

  • 80% of 10 marks is 8 marks.
  • 60% of 90 marks is 54 marks.
  • That is 62 marks out of 100 — 62%, not 70%.

The plain average was out by eight percentage points because it treated a 10-mark quiz as equal in importance to a 90-mark exam. Percentages only average directly when the groups behind them are the same size. Whenever they are not, enter the group sizes and use the weighted figure.

Both formulas

Sum of percentages ÷ How many

(80 + 60) ÷ 2 = 70%

The plain average. Correct only when every group is the same size.

Σ(Percentage × Group size) ÷ Σ(Group size)

((80×10) + (60×90)) ÷ 100 = 62%

The weighted average. Correct whenever the groups differ.

Worked example

Three stores convert at 4%, 6% and 9%, on 1,000, 500 and 100 visitors respectively. What is the overall conversion rate?

  1. Turn each percentage back into a count.40 + 30 + 9 = 79 conversions
  2. Add up the groups behind them.1,000 + 500 + 100 = 1,600 visitors
  3. Divide and multiply by 100.79 ÷ 1,600 × 100 ≈ 4.94%

Answer≈ 4.94% — not the 6.33% a plain average would suggest

Open this example in the calculator →

Where this comes up

  • Grades across papers — each worth a different number of marks.
  • Conversion rates across channels — each with very different traffic.
  • Survey results across regions — each with a different sample size.
  • Interest or return rates — across accounts holding different balances.
  • Defect rates across production runs — of different batch sizes.

If you are averaging exam marks specifically, the grade percentage calculator converts each paper first; bring the results back here with the mark allocations as group sizes.

Frequently asked questions

How do I calculate the average of percentages?
Add the percentages together and divide by how many there are. That plain average is only correct when each percentage describes a group of the same size — otherwise you need the weighted average.
Why can I not just average percentages?
Because a percentage hides the size of the group behind it. Scoring 80% on a 10-mark quiz and 60% on a 90-mark exam is not a 70% average — you scored 62 marks out of 100, so the real figure is 62%. The plain average treats the tiny quiz as equal to the huge exam.
What is a weighted average percentage?
It is the average after each percentage has been scaled by the size of the group it came from. Enter the group sizes in the second field and the calculator shows both figures side by side so you can see the gap.
How do I average percentages in Excel or Google Sheets?
For the plain average use =AVERAGE(A1:A5). For the weighted average use =SUMPRODUCT(A1:A5, B1:B5)/SUM(B1:B5), where column B holds the group sizes.
Can I average percentage increases?
Not with a plain average if you are compounding them over time — growth of 10% then 10% is 21% overall, not 20%. For a like-for-like set of independent percentages the average is fine.

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