Discount Calculator

How discounts work, and how stacked offers add up

A discount is a percentage taken off a price. The arithmetic is simple, but sales are designed to make it feel harder than it is, especially when several offers are layered together.

The formula

The amount saved is the original price multiplied by the discount percentage divided by 100. The sale price is the original price minus that saving. For a 120 item at 25% off, the saving is 30 and the sale price is 90.

A faster route is to multiply by what you keep. Paying 75% of the price means multiplying by 0.75, so 120 x 0.75 = 90. The same trick works for any discount: subtract the percentage from 100 and use the result as a decimal.

Why stacked discounts are not additive

When a store offers 20% off and then a further 10% off at the till, the second discount applies to the already reduced price. 100 becomes 80, then 72. The total discount is 28%, not 30%. The more discounts are layered, the further the combined figure falls short of the sum.

Using the calculator

1. 1Enter the original price before any discount.
2. 2Choose a preset discount or type your own percentage.
3. 3Add an extra discount if a coupon applies on top of the sale price.
4. 4Add sales tax or VAT if it is charged after the discount.

Judging whether a sale is a good deal

• Compare against the usual price, not the crossed-out one. A "50% off" label on an inflated reference price saves nothing.
• Compare unit prices when sizes differ. A smaller pack at a bigger discount can still cost more per gram.
• Ignore urgency. Countdown timers are a sales technique, not a price signal.
• Ask whether you needed it at the full price. A saving on something unwanted is still a cost.

Related calculators

The Percentage Decrease Calculator finds the discount from two prices, and the Percentage Calculator handles any other percentage question. For restaurant bills, see the Tip Calculator.