Percentage Calculator
Calculate percentages, increases, decreases & more
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Enter numbers to calculate
Free percentage calculator — four calculations in one
Toololis Percentage Calculator handles the four most common percentage questions in one place: X% of Y, X is what percentage of Y, percentage change from A to B, and adding/subtracting a percentage to a value. Live results as you type. Works on phones, tablets, and desktop.
The four percentage questions
- X% of Y — "What is 20% of 80?" → 16 (for tips, discounts, tax)
- X is what % of Y — "30 is what % of 150?" → 20% (for test scores, market share)
- % Change — "From 50 to 75?" → +50% (for price changes, performance)
- Add / Subtract % — "100 plus 15%?" → 115 (for tax, markup, discount)
How to use this tool
- 1
Choose a calculation type
Four tabs handle the four common percentage questions: X% of Y, X is what % of Y, percentage change, and after-percentage value.
- 2
Enter your numbers
Type into the two number fields. Results update live as you type — no need to click a button.
- 3
Read the result
The big number at the bottom is your answer. A plain-language sentence explains what it means.
Common real-life percentage calculations
- Restaurant tip — Bill $80, 18% tip: 80 × 0.18 = $14.40
- Sale discount — $120 item, 25% off: 120 × 0.75 = $90
- Sales tax — $50 + 8% tax: 50 × 1.08 = $54
- Test score — Got 42/50: (42/50) × 100 = 84%
- Stock gain — Bought $100, now $143: (143-100)/100 × 100 = 43% gain
- Salary raise — $50k + 8% raise: 50000 × 1.08 = $54,000
Frequently Asked Questions
How do I calculate X% of Y?
Multiply Y by X, then divide by 100. Example: 20% of 80 = (80 × 20) / 100 = 16. Use the first tab to do this automatically.
How do I find what percentage X is of Y?
Divide X by Y, then multiply by 100. Example: 30 is what % of 150? (30 / 150) × 100 = 20%. Use the second tab.
How do I calculate percentage change?
Subtract the old value from the new, divide by the old value, multiply by 100. Example: going from 50 to 75 is a (75-50)/50 × 100 = 50% increase. Negative results mean a decrease. Use the third tab.
How do I add X% to a value?
Multiply the value by (1 + X/100). Example: 100 plus 15% tax = 100 × 1.15 = 115. Tab four does this; negative percentages subtract.
Why does percentage math seem confusing?
People mix up "percentage of" with "percentage change". A 50% increase followed by a 50% decrease does NOT return to the original — you end up at 75% of the start. Always clarify which question you're asking.
Is this calculator accurate for financial use?
Yes, for standard percentage math. For complex finance (compound interest, tax brackets, discount stacking), use a purpose-built tool like a mortgage or tax calculator.
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