Percentage Calculator
Three common percentage calculations, done instantly and correctly.
Result:
Percentage Formulas Reference
X% of Y = (X ÷ 100) × Y
X is what % of Y = (X ÷ Y) × 100
Percentage change = ((New − Original) ÷ Original) × 100 — a positive result is an increase, negative is a decrease, always relative to the original value
Frequently Asked Questions
What's the difference between percentage change and percentage of a number?
'Percentage of a number' answers a static question (what is 20% of 150?). 'Percentage change' answers a comparison question (a value went from 150 to 180 — what's the percent change?) and the formula and interpretation are different — mixing them up is a common source of calculation errors.
Why is percentage decrease not simply the negative of percentage increase?
Percentage change is always calculated relative to the ORIGINAL value, not the new one. Going from 100 to 150 is a 50% increase, but going from 150 back to 100 is a 33.3% decrease (50/150), not 50% — the base value differs in each direction.
Is my data sent anywhere when I use this calculator?
No — all calculations happen instantly in your browser using plain JavaScript arithmetic; nothing is transmitted to a server.
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