How to use the discount calculator
- Enter the original price (before any discount).
- Enter the discount percentage, for example 20 for “20% off”.
- If the shop offers an extra discount on top — such as “an extra 10% off sale prices” or a coupon — enter it in the second box.
- Optionally add sales tax or VAT if it is charged at the till rather than included in the price.
The calculator shows the final price, the amount you save, and the effective discount — the single percentage that equals all your discounts combined.
The discount formula
Sale price = Original price × (1 − Discount ÷ 100)
You save = Original price − Sale price
Example: 20% off 2,500 → 2,500 × 0.80 = 2,000. You save 500.
Stacked discounts are not added together
“20% off plus an extra 10%” sounds like 30% off, but it is actually less. The second discount is taken from the already-reduced price:
2,500 × 0.80 = 2,000 → 2,000 × 0.90 = 1,800
The total saving is 700, which is an effective discount of 28%, not 30%. The general rule for two discounts a% and b% is:
Effective discount = 1 − (1 − a/100) × (1 − b/100)
Discount first or tax first?
In most places, sales tax is charged on the discounted price, so the calculator applies the discount first and then adds tax. Mathematically, the order does not change the final total for a percentage discount, but it does change how much tax you pay in money terms: tax on a lower price is lower. In countries where prices already include VAT (such as the UK, EU and Bangladesh retail prices), leave the tax box empty.
Working out the original price from a sale price
If you only know the sale price and the discount, divide instead of multiplying:
Original price = Sale price ÷ (1 − Discount ÷ 100)
A jacket that costs 1,800 after 25% off had an original price of 1,800 ÷ 0.75 = 2,400.
Shopping tips
- Compare the final price, not the percentage. “50% off” an inflated price can cost more than a fair price elsewhere.
- For “buy one, get one 50% off”, the effective discount across both items is 25%.
- Remember delivery charges and tax when comparing an online deal with a shop price.
Frequently asked questions
How do I calculate 20% off a price?
Multiply the price by 0.80 (which is 1 − 0.20). For example, 20% off 2,500 is 2,500 × 0.8 = 2,000.
Is 20% plus 10% off the same as 30% off?
No. The second discount applies to the reduced price, so 20% then 10% equals a 28% total discount.
Should tax be added before or after the discount?
Usually after. Sales tax is normally charged on the price you actually pay, which is the discounted price.
How do I find the discount percentage from two prices?
Subtract the sale price from the original price, divide by the original price, and multiply by 100. Our percentage calculator can do this for you.