Percentages show up everywhere — 30% off, 15% tip, "up 8% year over year", 72% on the final exam. Mental math works for simple cases; a percentage calculator saves mistakes when decimals stack up.
Four problems people search most
1. What is X% of Y?
Example: 20% of $85 sale item → $17 off.
Use case: shopping, tax estimates, commission.
2. X is what percent of Y?
Example: 42 correct out of 50 questions → 84%.
Use case: grades, survey results, completion rates.
3. Percent increase or decrease
Example: Stock went from $40 to $46 → 15% increase.
Use case: inflation, salary raises, KPI dashboards.
4. Add or subtract a percent
Example: $120 + 8% sales tax, or price after 25% markdown.
Use case: receipts, invoices, markdown pricing.
Quick mental shortcuts (when you are offline)
| Trick | Example |
|---|---|
| 10% = move decimal left once | 10% of 240 = 24 |
| 5% = half of 10% | 5% of 240 = 12 |
| 15% = 10% + 5% | 15% of 240 = 36 |
For stacked discounts (20% then another 10%), use the tool — they do not add linearly.
Related math tools on CalculatorFree
- Tip calculator — split bill + gratuity
- Fraction calculator — convert ratios
- Grade calculator — weighted course average
- Scientific calculator — expressions beyond percent
Full catalog: CalculatorFree.Online
Try the percentage calculator
Enter two values, pick the operation, get the result without spreadsheet setup.
Estimates for everyday use. Verify financial figures with primary documents.
