% Percentage Calculator

Calculate percentages instantly: what is X% of Y, Y is what percent of X, percentage change, and more — all in your browser.

What is X% of Y?

% of

Y is what % of X?

of

Percentage change (from → to)

→

Add / subtract a percentage

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How it works

Formulas used

  • X% of Y: result = Y × X / 100
  • Y is what % of X: result = Y / X × 100
  • Percentage change: change = (to − from) / from × 100. Positive = increase, negative = decrease. Note: when from is negative, sign follows standard mathematical convention.
  • Add / subtract percentage: result = value ± (value × pct / 100)
Privacy & Security

All calculations are performed locally in your browser using JavaScript arithmetic. No data is transmitted to any server.

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Accuracy, Limits & Tips
  • Percentage change from zero is undefined — the tool will warn you.
  • Results are shown to up to 10 significant figures (JavaScript IEEE 754 double precision).
  • Very large or very small numbers may appear in scientific notation.
Examples
  • What is 15% of 340? → 51
  • 75 is what % of 300? → 25%
  • Percentage change from 80 to 100 → 25% increase
  • 120 + 10% → 132
  • 200 − 20% → 160

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