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Math

Percentage Calculator

Solve common percentage problems: find X% of Y, determine what % X is of Y, calculate percentage change, increase/decrease a number by a percentage, and recover the original value from a final amount and % change. All calculations run locally in your browser.

Quick Percentage Math
Client-side onlyFast & private
Calculation

Choose the type of percentage calculation you need.

Options
Status
X% of Y

Set inputs below and view instant results.

Percent (X)
Base (Y)

Results

X% of YDecimals 2
Summary
  • Percent: 25.00%
  • Base (Y): 200.00
  • Result: 50.00

Result = (X ÷ 100) × Y

Tips

For “what % is X of Y” and “% change,” results are undefined when the denominator is zero. Adjust decimals for currency-friendly rounding.

Percent addition and subtraction are relative to the base: increasing by 10% then decreasing by 10% does not return to the original value.

How to Use the Percentage Calculator

This free, client-side Percentage Calculator solves the most common % problems: X% of Y, what percent, percentage change, increase/decrease by %, and find original from final. Nothing is uploaded.

  1. Pick a calculation: Choose from the dropdown (e.g., “X% of Y” or “% change”).
  2. Enter numbers: Fill in the required fields (the labels change per calculation).
  3. Set decimals: Control rounding for currency or precise values.
  4. Read the result: The tool updates instantly and shows the formula used.
  5. Copy or reset: Use Copy to save results, Reset to start over.

Formulas

  • X% of Y: (X ÷ 100) × Y
  • What % is X of Y: (X ÷ Y) × 100
  • % change (A → B): ((B − A) ÷ A) × 100
  • Increase by %: Y × (1 + X/100)
  • Decrease by %: Y × (1 − X/100)
  • Original from final & increase: Final ÷ (1 + X/100)
  • Original from final & decrease: Final ÷ (1 − X/100)

Examples

  • 15% of 200 → 30
  • What % is 30 of 120 → 25%
  • Percent change 120 → 150 → 25%
  • Increase 200 by 12.5% → 225
  • Final 120 after 20% increase → Original 100

FAQ

Why is the result “—”?

Some calculations are undefined when dividing by zero (e.g., “what % is X of 0”). Enter a non-zero base/starting value.

Can I do multiple steps?

Yes—use the results as inputs for the next calculation (e.g., increase by 10% then find the % change).

Is my data private?

Absolutely. This calculator runs entirely in your browser. No data is uploaded or stored.