How to use this percentage calculator
- X% of Y: Enter the percent in X and the base number in Y. Result is (X / 100) × Y.
- What percent is A of B: Enter A and B, then compute (A / B) × 100.
- Increase/Decrease by X%: For increase, multiply by (1 + X/100). For decrease, multiply by (1 − X/100).
Common examples
| Scenario | Formula | Example |
|---|---|---|
| Discount price | Price × (1 − d%) | $80 at 25% off → 80 × 0.75 = $60 |
| Sales tax | Subtotal × (1 + t%) | $120 with 7% tax → 120 × 1.07 = $128.40 |
| Grade share | (A / B) × 100 | 45 out of 60 → 75% |
| Percent change | ((new − old) / old) × 100 | 200 → 220 = 10% increase |
Tips for accurate results
- Round money to two decimals for receipts and reports.
- Stacking percentages is not additive (e.g., +10% then −10% ≠ 0%).
- When B = 0 in “what percent is A of B,” the operation is undefined.