Discount Calculator
Enter an original price, sale price or discount to work out how much you save. Add extra discounts, a fixed amount off, tax or quantity when you need a fuller price estimate.
Your sale price
A larger percentage off does not necessarily mean the lowest final price. Compare final total, shipping, fees, quantity and product terms before buying.
Price breakdown
| Step | Amount |
|---|---|
| Original price | £80.00 |
| First discount — 25% off | −£20.00 |
| Sale price per unit | £60.00 |
| Sale subtotal before tax | £60.00 |
This calculator works out prices from the discount and tax values you enter. It does not check retailer pricing, coupon rules, product availability, local tax rules, shipping, delivery, fees or whether an offer is the best value.
How to use this calculator
- Choose what you know: an original price and a discount, an original price and a sale price, or a sale price and a discount.
- Enter your prices. In the first mode, choose a percentage or a fixed amount off, and use the quick percentage buttons if one matches the discount shown by the seller.
- Open Add more discounts to stack up to two further percentage discounts and one more fixed amount off — each is applied to the already-reduced price, in order.
- Enter a quantity if you are buying more than one, to see the subtotal for all of them.
- Open Add tax after discount if you want a tax percentage or amount added to the sale price, applied after every discount.
- Read the sale price, savings and effective discount below the form, along with the full step-by-step breakdown.
How is a discount calculated?
A percentage discount is the original price multiplied by the discount rate; the sale price is what remains after that amount is taken off.
- discount amount = original price × discount % ÷ 100
- percentage off = (original price − sale price) ÷ original price × 100
- original price = sale price ÷ (1 − discount % ÷ 100)
- a fixed amount off is capped so the price cannot go below zero
- tax, if entered, is applied after every discount, not before
For example, 25% off an £80 item is a discount of £80 × 25 ÷ 100 = £20, giving a sale price of £80 − £20 = £60. The same maths works in reverse: a $72 sale price after 20% off implies an original price of $72 ÷ (1 − 0.20) = $90.
How do stacked discounts work?
Each extra percentage discount is calculated on the price that is already reduced, not on the original price, and not simply added to the first percentage. Two 20% discounts on $100 give $100 × (1 − 0.20) × (1 − 0.20) = $64 — a 36% total discount, not 40% off. A fixed amount off is always applied last in this calculator, after every percentage discount, and is capped at whatever price remains so the sale price is never negative.
Working out a single discount by hand? The Percentage Calculator covers the plain percentage-of-a-number maths behind the first step here.
Assumptions and what this calculator does not do
- Prices are treated as pre-tax, pre-shipping and pre-fee unless you enter a tax figure.
- Discounts are applied in a fixed, sequential order — never simply added together.
- A fixed discount is capped at the current price and never produces a negative sale price.
- Tax, when entered, is a manual percentage or amount applied after every discount, not a looked-up rate.
- Every unit is assumed to be discounted identically; quantity multiplies the per-unit result.
- Coupon codes, multi-buy offers, shipping, delivery fees, retailer rules and currency conversion are not included.
Pricing a markup instead of a discount? See the Markup Calculator. Splitting a bill that already includes a discount, service charge or tip? See the Tip Calculator.