Average Percentage Calculator
Work it out instantly, with the formula shown.
Inputs
| Percentage | Weight | Share |
|---|---|---|
| 80% | 1 | 33.33% |
| 90% | 1 | 33.33% |
| 75% | 1 | 33.33% |
The formula
weighted average = Σ(percent × weight) ÷ Σweight
Averaging percentages needs care
You can only average percentages directly when they are all out of the same total. Scoring 80% on a 10-mark test and 90% on a a 100-mark test does not average to 85% — the second test carries ten times the weight, giving 89.1%. Enter the mark totals as weights to get that right.
What a percentage is
"Per cent" means "per hundred", so a percentage is just a fraction with 100 on the bottom. 15% is 15/100, which is 0.15 as a decimal. Every percentage calculation is therefore multiplication or division by a decimal — the percent sign is bookkeeping, not a new operation.
The three questions
Almost every percentage problem is one of three:
- What is P% of N? Multiply:
N × P/100 - A is what percent of B? Divide:
A/B × 100 - A is P% of what? Divide the other way:
A ÷ (P/100)
Recognising which one you have is most of the work; the arithmetic is straightforward once you do.