Percentage Calculator
Three calculation modes. Instant results. No clutter.
What is X Percent of a Number?
Your manager emails at 9 AM: "We hit 73% of the quarterly target. What's the actual number?" The target was $420,000. You need the answer before the standup in ten minutes. Enter 73 in the percentage field and 420000 in the number field. Result: $306,600 — in under a second.
Example: (15 ÷ 100) × 200 = 30
X is What Percent of Y?
You scored 42 out of 56 on a test and need the grade percentage before the class average gets posted. Enter 42 in the first field and 56 in the second. Result: 75% — exactly what you need for the grade calculator.
Example: (30 ÷ 200) × 100 = 15%
Calculate Percentage Change
Your electricity bill went from $148 last month to $186 this month. Is that a big jump or normal? Enter 148 in "From" and 186 in "To." Result: +25.68% increase — now you know it's worth investigating.
Example: ((250 − 200) ÷ 200) × 100 = +25%
Quick Reference — Common Percentage Results
| Percentage | Of | Result |
|---|---|---|
| 1% | 1,000 | 10 |
| 5% | 1,000 | 50 |
| 10% | 1,000 | 100 |
| 15% | 200 | 30 |
| 20% | 150 | 30 |
| 25% | 80 | 20 |
| 30% | 500 | 150 |
| 50% | 200 | 100 |
| 75% | 400 | 300 |
| 100% | 250 | 250 |
Common Mistakes to Avoid
✗ Entering 0.15 instead of 15 for 15%
✓ This calculator expects the percentage as a whole number (15, not 0.15). Entering 0.15 gives you 0.15% of the number — 100× smaller than intended.
✗ Confusing "X% off" with "X% of"
✓ "15% of $200" = $30 (the percentage amount). "15% off $200" = $200 − $30 = $170 (the price after discount). This calculator shows you both the result and the remainder.
Frequently Asked Questions
15% of 200 = 30. Use the "What is X% of Y?" tab: enter 15 in the percentage field and 200 in the number field. The formula is (15 ÷ 100) × 200 = 30.
Use the "X is what % of Y?" tab. Divide the first number by the second and multiply by 100. Example: 30 is what percent of 200? (30 ÷ 200) × 100 = 15%.
Use the "Percentage Change" tab. The formula is ((New − Old) ÷ Old) × 100. Example: from $200 to $250 is a +25% increase. From $250 to $200 is a −20% decrease.
20% of 150 = 30. The remainder is 120 (80% of 150). Practical use: a 20% tip on a $150 bill is $30, making the total $180.
For 10%: move the decimal one place left ($84 → $8.40). For 15%: find 10% and add half ($8.40 + $4.20 = $12.60). For 20%: double the 10% value ($8.40 × 2 = $16.80). This calculator does it instantly for any percentage.
Last updated: January 15, 2025 · Formula source: NIST Weights and Measures