Calculate a percent of a number, a part as a percent of a whole, or signed percentage change.
Enter values, then calculate.
How the calculation works
Choose the mode. Percent of a number = p÷100×value. Part as a percent = part÷whole×100. Change = (new−old)÷|old|×100, preserving the source convention for negative starting values. A positive change is labeled increase, negative decrease, and zero no change. Output uses up to four decimal places.
Example and verification
20% of 85 is 17; 36 out of 40 is 90%; 1,000 to 1,500 is a 50% increase. Under the absolute-baseline convention, −100 to −50 is also a 50% increase. Tests reject a zero whole or zero starting value.
Software checks cover the example, invalid input, zero or boundary cases, and reset in Chromium. No physical measurements or all-browser certification are claimed.
Scope and limitations
Percentage change from zero is undefined. Negative baselines have several conventions; this tool explicitly uses the absolute starting value. Percentage points are a different measure: 10% to 12% is +2 percentage points but +20% relative change. JavaScript floating-point and display rounding may affect final digits.
Common questions
Can percentages exceed 100%?
Yes for a part larger than its whole or for growth. This math tool permits it; a shopping discount has a separate 0–100% range.
Technical references
Related calculators
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Maintained by GadgetsFocus. Updated 2 October 2026 with AI-assisted writing and translation review; no human native-speaker or clinical review is claimed.