Percentage Calculator
Find any percentage in seconds — what X% of a number is, percent change between two values, and more.
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How to Use the Percentage Calculator
Choose one of the four modes at the top of the calculator, enter your two numbers, and the answer appears instantly — no buttons to press. The result updates live as you type, so you can experiment freely: nudge a discount from 20% to 25% and watch the final price move in real time.
- X% of Y — the classic: find a portion of a number. Example: a 15% tip on a $200 bill.
- X is what % of Y — reverse lookup: 30 is what percent of 200?
- Percent change — how much a value grew or shrank: from 200 to 250 is +25%.
- X is Y% of what? — find the whole: 30 is 15% of what number? (Answer: 200.)
Percentage Formulas Explained
A percentage is simply a fraction of 100. The word comes from the Latin per centum — "per hundred." Every percentage calculation below is a variation of one idea: part ÷ whole × 100.
To convert a percentage to a decimal you can multiply with, just divide by 100: 15% becomes 0.15, 7.5% becomes 0.075. To go the other way, multiply a decimal by 100: 0.2 becomes 20%.
Percent Increase & Decrease: Worked Examples
Example 1 — Percent increase
Your rent goes from $1,200 to $1,320 per month. What is the percent increase?
Step 1: Find the difference: $1,320 − $1,200 = $120.
Step 2: Divide by the original: $120 ÷ $1,200 = 0.10.
Step 3: Multiply by 100: 0.10 × 100 = 10% increase.
Example 2 — Percent decrease
A jacket drops from $80 to $60 in a sale. What is the percent decrease?
Step 1: Difference: $80 − $60 = $20.
Step 2: Divide by the original: $20 ÷ $80 = 0.25.
Step 3: Multiply by 100: 25% decrease — you save a quarter of the price.
Example 3 — Increase then decrease (the trap)
A $100 stock rises 50% to $150, then falls 50%. Many people expect $100 back — but 50% of $150 is $75, so the stock lands at $75. Percentages don't "cancel out" because the base changes. This asymmetry is why investors fear drawdowns: a 50% loss needs a 100% gain to recover.
Common Percentage Calculations
| Question | Answer | How |
|---|---|---|
| 20% of 150 | 30 | 150 × 0.20 |
| What % is 45 of 180? | 25% | 45 ÷ 180 × 100 |
| Increase 200 by 15% | 230 | 200 × 1.15 |
| Decrease 200 by 15% | 170 | 200 × 0.85 |
| 50 is 20% of what? | 250 | 50 ÷ 0.20 |
| Change from 80 to 100 | +25% | (100−80) ÷ 80 × 100 |
Two shortcuts worth memorizing: to add X%, multiply by (1 + X/100) — e.g., ×1.15 for +15%. To subtract X%, multiply by (1 − X/100) — e.g., ×0.85 for −15%.
Percentage vs Percentile vs Percentage Point
These three sound alike but mean very different things — mixing them up is one of the most common math errors in news reporting.
- Percentage — a share of a whole. "60% of voters" means 60 out of every 100.
- Percentage point — the arithmetic difference between two percentages. If support rises from 40% to 45%, that's a 5 percentage point increase — but a 12.5% relative increase (5 ÷ 40). Always clarify which one a headline means.
- Percentile — a ranking. Scoring in the 90th percentile means you beat 90% of the group; it says nothing about your absolute score.
When someone says "increased by 200%," they mean it tripled (original + 2× original) — another classic source of confusion. If precision matters, state the before-and-after numbers, not just the percent.
My saved numbers reuse them in any calculator
Save a number once — like your rent or hourly rate — then just type its name instead of the number, in any calculator here. You can also type formulas like 5000 * 1.1 right into any box.
Saved only in this browser — nothing is sent to us.
Frequently Asked Questions
How do I calculate a percentage?
Convert the percentage to a decimal and multiply. For example, 20% of 150 is 0.20 × 150 = 30. Our calculator does this instantly — just enter the percent and the number.
What is 20% of 150?
20% of 150 is 30. Calculation: 150 × 0.20 = 30.
How do I find percent increase?
Subtract the old value from the new value, divide by the old value, then multiply by 100. For example, going from 200 to 250: (250 − 200) ÷ 200 × 100 = 25% increase.
What is the formula for percentage change?
Percentage change = (New Value − Old Value) ÷ |Old Value| × 100. A positive result is an increase; a negative result is a decrease.
How do you calculate percent off a price?
Multiply the price by the discount as a decimal, then subtract from the original price. For 25% off $80: $80 × 0.25 = $20 discount, so you pay $60.