How the sale price is worked out
Sale price = original price × (1 − discount ÷ 100)
So 20% off 250 is 250 × 0.8 = 200.
Stacked discounts are applied one after the other. “20% off, plus an extra 10% at the till” means the 10% comes off the already reduced price. The total discount is 28%, not 30%. The calculator shows the true overall discount so you can compare offers fairly.
Questions people ask
Is 20% off plus 10% off the same as 30% off?
No. The extra 10% is taken from the reduced price, so the overall discount is 28%. On 100, that's 72 instead of 70.
How do I work out the original price from a sale price?
Divide the sale price by (1 − discount ÷ 100). A price of 200 after 20% off was originally 200 ÷ 0.8 = 250.
Does this include sales tax or VAT?
No. It works on whatever price you enter. To add tax afterwards, use the VAT calculator on the sale price.