How to use the discount calculator
Each box answers a different shopping question. Type your numbers and the results update immediately, with the calculation shown underneath. Any currency works.
- Price after discount: the sale price and your savings. Add an extra discount for offers like “an extra 10% off sale items”, and a tax rate to see the final price at the checkout.
- What percent off is it?: compare the original and the sale price to see the real discount.
- Original price: work backwards from a sale price and the discount.
- Add or remove tax: add sales tax or VAT to a price, or find the price before tax from a price that already includes it.
Discount formulas
- Sale price = original price × (1 − discount ÷ 100). Example: 80 with 25% off = 80 × 0.75 = 60.
- Percent off = (original − sale price) ÷ original × 100. Example: from 80 to 56 is (80 − 56) ÷ 80 = 30% off.
- Original price = sale price ÷ (1 − discount ÷ 100). Example: 48 after 20% off was 48 ÷ 0.8 = 60.
- Price with tax = price × (1 + tax rate ÷ 100). Price before tax = price with tax ÷ (1 + tax rate ÷ 100).
FAQ
Is 20% off plus an extra 10% off the same as 30% off?
No. The second discount is taken from the already reduced price, so 20% and then 10% off equals 28% off: 100 × 0.8 × 0.9 = 72.
Why can’t I remove tax by subtracting the tax rate?
Because the tax was calculated on the lower price before tax. With 20% VAT, a price of 120 includes 20 of tax (120 ÷ 1.2 = 100), not 24 (20% of 120).
Is the discount taken before or after tax?
In most shops the discount is applied to the price first and tax is added to the reduced price. Mathematically the final amount is the same either way, as long as both are percentages.