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Percentage Calculator

Three quick percentage calculators: % of a number, what % is X of Y, and percent change.

  • percent
  • percentage
  • %
  • discount
  • increase
  • change

About Percentage Calculator

"Percentage" gets used to mean three different but related calculations in everyday life. There's "what is 20% of $150?" (a tip or a discount), "30 out of 150 is what percent?" (a test grade or a market share), and "the price went from $80 to $100 — what's the percent change?" (a stock move or a price increase). The formulas are simple individually, but figuring out which one matches the question in front of you is where most percentage mistakes come from.

This page gives you all three side by side, each with its own clearly-labelled inputs and result. No need to remember which version multiplies and which version divides, and no risk of accidentally calculating a markup as a markdown.

How to use

Pick the calculator that matches your question.

For "What is X% of Y?", enter the percent and the base — handy for tips, discounts, sales tax, and commissions. For "X is what % of Y?", enter the part and the whole — useful for grades, ratios, and progress against a target. For "Percent change from X to Y", enter the starting and ending values — the result is shown in green for increases and red for decreases, with a + or − sign for clarity. Every result has a copy button beside it.

Frequently asked questions

  • How do I work out a tip?

    Use the "What is X% of Y?" calculator: enter the tip percent (typically 15–20% in North America) and the bill total. The result is the tip amount; add it to the bill for the total to pay. For round-number bills, halving 20% gives 10% — so 18% of $50 is roughly $9.

  • What's the difference between percentage change and percentage point change?

    Percentage change is relative: going from 5% to 10% is a 100% increase. Percentage point change is absolute: going from 5% to 10% is a 5-percentage-point increase. Politicians and journalists sometimes blur the two; this calculator gives the relative percent change.

  • How does a percent increase followed by an equal percent decrease work out?

    Not back to where you started. A 20% increase followed by a 20% decrease leaves you 4% lower than the original (because the second percentage is applied to the bigger intermediate value). This is why sales of "20% off, then another 10% off" don't equal "30% off".

  • Can the percent change be negative?

    Yes. Going from 100 to 80 is a −20% change. The calculator shows decreases in red with a minus sign, increases in green with a plus sign, so the direction is obvious at a glance.

  • How do I reverse a discount — find the original price from the discounted one?

    Use "X is what % of Y?" with the discounted price as X and the original as Y… or, if you know the discount percent, divide the discounted price by (1 − discount/100). A $40 item at 20% off was originally $40 / 0.80 = $50.

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