Discount Calculator

How to use the Discount Calculator

1. Pick what you want to work out — the sale price, the original price, or the percentage off.
2. Enter the two figures. For stacked offers, add the second discount in the optional field.
3. Press Calculate to see the final price and the true effective discount.

Stacked discounts do not add up

"40% off, plus an extra 20% off sale prices" is not 60% off. The second discount applies to the already-reduced price, so the calculation is multiplicative:

100 × 0.60 = 60      (40% off)
 60 × 0.80 = 48      (a further 20% off)
Effective discount = 52%, not 60%

The gap widens as the discounts grow. Two 50% discounts give 75% off, never 100%. This tool shows the effective figure whenever you enter a second discount.

Working backwards from a sale price

To recover the original price, divide rather than add the percentage back. A jacket at 90 after 25% off was 90 ÷ 0.75 = 120. Adding 25% to 90 gives 112.50, which is wrong — because the 25% was calculated on 120, not on 90.

This is also how to check an advertised claim. If a shop shows "was 200, now 150", the real discount is (200 − 150) ÷ 200 = 25%.

Reading a sale honestly

A few things worth checking before deciding a discount is a bargain:

• What the reference price means. "Was" prices sometimes refer to a manufacturer's suggested price the item never sold at.
• Whether tax comes before or after. Discounts are normally applied to the pre-tax price, so the saving on your receipt looks smaller.
• Buy-one-get-one offers. BOGO is 50% off across two items, and "buy two get one free" is 33% off across three — only if you wanted all of them.

Frequently asked questions