Percentage Calculator — X% of Y, What % of, Reverse %, % Change

Instant results. Private by design—everything runs locally in your browser.

Calculations

Find X% of Y

Tips, discounts, VAT, markups—enter a percent and a base.

%
?

What percent is A of B?

Great for test scores, statistics, ratios, tax rates.

?

Reverse a Percentage (Find the Original Number)

If A is B% of the original, what was the original?

% of what?

Percent Increase/Decrease

Percent change = (New − Old) ÷ Old × 100.

Quick Reference

  • X% of Y → (X / 100) × Y
  • What % is A of B → (A / B) × 100
  • Reverse % (“A is B% of what?”) → A ÷ (B / 100)
  • % Change → ((New − Old) / Old) × 100

Tip: Press Ctrl/Cmd + K to focus site search.

Frequently Asked Questions

How do I calculate percent increase or decrease?

Use: (New − Old) ÷ Old × 100. Positive means increase; negative means decrease.

What’s the difference between “X% of Y” and “What percent is A of B”?

“X% of Y” multiplies Y by a percentage. “What percent is A of B” divides A by B and converts to a percentage.

Can I reverse a discount with this tool?

Yes. Use “A is B% of what?” to find the original price before a discount.

Are my inputs private?

Absolutely. Everything runs locally in your browser—no uploads.

Explore more tools