Discount Calculator
Discount percentage calculator: the price after a percent or amount off, the discount from two prices, a second discount stacked correctly, and sales tax.
Every convention this page applies is named in the result rather than assumed. Your numbers stay in this browser.
Results
How to read this: the verdict describes how much room your numbers leave, not a decision or an offer. Change any input to see how much the result moves.
Assumptions and formula
The sale price is the original less the discount. A second percentage is taken from the price after the first, which is how shops apply "an extra 10% off", so the combined discount is less than the sum: 20% then 10% is 28%. Tax is charged on the sale price and shown as its own line, and quantity multiplies the final figures only.
Amounts are held to full precision and rounded to the cent only when displayed, so the retailer’s own rounding may differ by a cent. Where the shelf price already includes VAT, as in the UK and EU, leave the tax rate at zero: the discount comes off the tax-inclusive price.
Worked example
A $100 jacket at 20% off is $80. An extra 10% off comes off the $80, not the $100: $8, leaving $72 — 28% off in all, not 30%. In a state with 8% sales tax the till charges 8% of $72, which is $5.76, for a total of $77.76.
Frequently asked questions
Is 20% off plus an extra 10% off the same as 30% off?
No — it is 28% off. The extra 10% is taken from the price after the first discount, not from the original. On $100, 20% off leaves $80, and 10% of $80 is $8, so you pay $72. A straight 30% would be $70. The gap grows with bigger discounts: 50% then 50% is 75% off, not free. This calculator reports the combined figure and the naive sum side by side.
Is sales tax charged before or after the discount?
After. In the US, sales tax is charged on the amount you actually pay, so a $100 item at 20% off in an 8% tax state is $80 plus $6.40 tax, $86.40. In the UK and EU the shelf price already includes VAT, so a 20% discount on a £100 price tag is £80 at the till and the tax line is zero here. Enter the tax rate only where tax is added at checkout.
How do I work out the percentage off from two prices?
Subtract the sale price from the original, divide by the original, and multiply by 100. A jacket marked down from $80 to $60 is (80 − 60) ÷ 80 = 25% off. Dividing by the sale price instead gives 33% and is the most common mistake; the "find the discount" mode here divides by the original.
How do I find the original price from the sale price and the discount?
Divide the sale price by (1 − the discount as a decimal). A $60 sale price at 25% off means the original was 60 ÷ 0.75 = $80. Adding 25% back to $60 gives $75 and is wrong, because the 25% was a share of the larger original, not of the sale price. The percentage calculator’s reverse mode does this directly.
How does a percent off calculator work out the sale price?
Multiply the price by (1 − the discount as a decimal). A £80 jacket at 25% off is £80 × 0.75 = £60, and the saving is £20. Working the other way, a percent off calculator finds the discount from two prices: £60 from £80 is a 25% reduction. Where it goes wrong is stacking: 25% off then a further 10% off is £80 × 0.75 × 0.9 = £54, a 32.5% discount, not 35%. This page shows each step so the stacked result is never a surprise at the till.
How much is 20 percent off, and what about a double discount?
Twenty percent off means you pay 80% of the price: on £50 that is £40, a saving of £10, which is all a 20 percent off calculator does. A sale price calculator is the same arithmetic with any percentage. A double discount calculator handles the case that trips people up: 20% off, then a further 15% off at the till, is £50 × 0.8 × 0.85 = £34, a 32% discount, not 35%, because the second percentage comes off the already reduced price. The price after discount calculator on this page shows each step and then adds sales tax to the final figure.