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Percentage Calculator

Percent of, change, discounts and tax

Work out percentages, percentage change, discounts, margins and markups, and add or remove GST/VAT.

How to use Percentage Calculator

  1. Find the card for your question: X% of Y, X is what % of Y, percentage change, add or subtract X%, reverse percentage, discount, margin vs markup, GST / VAT, or percentage points.
  2. Type your numbers into that card. The result updates as you type, and the formula used is shown under it.
  3. For a stacked discount, list the percentages separated by commas, such as 20, 10. For GST or VAT, choose whether your amount includes tax, then pick a rate preset (5, 12, 18, 28) or type your own.
  4. Switch the GST card to CGST + SGST to see the tax split into two equal halves.
  5. Use Copy share link to send the current values of every card to someone else.

How it works

Each card is a one-line formula evaluated with ordinary floating-point numbers, for example Y × X ÷ 100 or (B − A) ÷ |A| × 100. Results are rounded for display only, to 2 decimal places (4 for the plain percent cards), rounding halves away from zero, so 1.005 shows as 1.01.

Stacked discounts apply one after another, each to the already-reduced price, so 20, 10 is a 28% discount overall, not 30%. Margin is profit divided by the selling price and markup is profit divided by cost, so 25% markup is 20% margin. For GST or VAT the tax is rounded to 2 decimals and the net or gross follows from it; CGST and SGST are each half of the tax, with any odd paisa going to SGST.

Everything runs in your browser.

Limits

  • Inputs are plain decimals with an optional sign; thousands commas are ignored, but exponent notation such as 1e5 is not accepted.
  • Percent change from 0, X is what % of 0, a margin of 100% or more, and reversing a 100% decrease are undefined and show a message instead of a number.
  • Percent change divides by the absolute value of the starting number, so changes from negative numbers read in the direction of the move.
  • Results use floating-point arithmetic, so extremely large values lose precision beyond about 15 digits.
  • The GST card rounds to 2 decimals (currency units); it does not apply country-specific rounding rules or tax slabs.

Privacy

Calculations run entirely in your browser; nothing is uploaded or stored, and the site’s Content Security Policy blocks requests to other servers. Copy share link puts the values in the link’s # fragment, which browsers don’t send to servers.

Frequently asked questions

What is the difference between margin and markup?

Markup is profit as a percentage of cost; margin is profit as a percentage of the selling price. Buying at 80 and selling at 100 is a 25% markup but a 20% margin.

Why are two discounts of 20% and 10% not 30% off?

The second discount applies to the price after the first, so 1000 becomes 800 and then 720: a 28% saving overall. Use the discount card with 20, 10 to see it.

How do I remove GST from a price that already includes it?

Choose Including tax on the GST / VAT card. The net price is the amount divided by 1 plus the rate (1180 at 18% gives 1000), not the amount minus 18%.

What are percentage points?

The plain difference between two percentages. A rate rising from 10% to 12% is 2 percentage points, but a 20% relative increase.

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