ToolPikaHow it works
Each row answers a different question. All three use the same idea: a percentage is a number out of 100.
| Question | Formula | Example |
|---|---|---|
| What is P% of V? | V × P ÷ 100 | 20% of 150 = 150 × 20 ÷ 100 = 30 |
| A is what percent of B? | A ÷ B × 100 | 30 ÷ 150 × 100 = 20%, so 30 is 20% of 150 |
| A is P% of what? | A ÷ P × 100 | 30 ÷ 20 × 100 = 150, so 30 is 20% of 150 |
The results are rounded to 10 decimal places to hide floating-point noise (so 0.1 + 0.2 shows as 0.3, not 0.30000000000000004). Division by zero is reported instead of showing an invalid result.
Examples
Sales tax. An item costs 64 and tax is 8%. 8% of 64 is 5.12, so the total is 69.12.
Exam score. You got 27 questions right out of 32. 27 is 84.375% of 32.
Working backwards from a deposit. You paid a 250 deposit, which was 20% of the price. 250 is 20% of 1,250, so the full price is 1,250.
Tip. A 15% tip on a 48 bill: 15% of 48 is 7.20.
Which row do I need?
- You know the percentage and the total, and want the amount → first row.
- You know two amounts and want the percentage → second row.
- You know an amount and the percentage it represents, and want the total → third row.
If you want to know by how much a value went up or down between two numbers (for example, a price rising from 80 to 92), that is a percentage change, which uses a different formula: (new − old) ÷ old × 100.