Percentage Calculator Online Free
Three percentage modes: find a percentage of a number, find what percentage one number is of another, or calculate percentage change.
How this percentage calculator handles eight different question types with one small set of formulas
Percentage questions come in more shapes than people expect. Finding 25% of 200 is a different operation from asking what percent 50 is of 200, which is different again from asking what number, after a 15% increase, becomes 230. This tool covers all eight common phrasings as separate tabs, each wired to its own formula, rather than forcing every question through a single generic calculation that gets the algebra wrong for half the cases.
All eight modes run as plain arithmetic in your browser. There is no server round trip, the result updates the instant you change either number.
The core relationship behind every mode
Every percentage question is a rearrangement of one equation: part equals percent, expressed as a decimal, times whole. Which of the three quantities, part, percent, or whole, is missing determines which mode you need and how the formula gets rearranged to solve for it.
| Question type | Formula | Example |
|---|---|---|
| 25% of 200 | (25/100) × 200 | 50 |
| 50 is what % of 200 | (50/200) × 100 | 25% |
| Change from 80 to 100 | ((100−80)/80) × 100 | +25% |
| 200 increased by 15% | 200 × 1.15 | 230 |
| 230 is 15% more than what | 230 / 1.15 | 200 |
Verification step included
Modes that solve for a hidden base value, like “X is Y% more than what,” show a verification line that reapplies the percentage to the computed base and confirms it lands back on the original number you entered.
Guarded against division by zero
Modes 2, 3, 6, 7, and 8 all involve a division. The tool checks for a zero denominator, including the specific case of exactly 100% in the reverse modes, before calculating, and shows a clear message instead of a silent NaN.
- Percentage covers the general mathematical definition and notation this tool implements.
- Relative change and difference explains the asymmetry between percent increase and percent decrease used in modes 3 through 8.
Percentage questions people get wrong
Working out a discount at checkout, calculating a tip or sales tax, figuring out how much a salary changed year over year, reverse engineering an original price from a sale price and a known discount percentage, and checking whether a reported statistic such as sales grew 12 percent, was calculated against the correct base period. Anywhere a number is being compared against another number as a proportion, one of these eight modes almost certainly matches the question being asked.
Questions About Percentage Calculator Online Free
Yes. Completely free with no signup, no limit and no data sent anywhere.
Select Mode 1 (What is X% of Y). Enter 20 as the percentage and 500 as the number. Result: 100.
Select Mode 2 (X is what % of Y). Enter 75 and 300. Result: 25%.
Select Mode 3 (Percentage Change). Enter 80 as the original and 100 as the new value. Result: 25% increase.
Percentage change = ((new value minus original value) divided by original value) multiplied by 100.
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