How the Percent Off Calculator Works
Stores show discounts as a percentage: 20% off, 50% off, an extra 10% with a code. The Percent Off Calculator turns those numbers into the amounts that matter: what you will pay, how much you save, and what the price was before the sale. It has three modes, so you can start from whatever you know.
Mode 1: find the sale price
Enter the original price and the percent off. The calculator takes the discount away from the price:
savings = original price x percent off / 100 sale price = original price - savings
For example, 20% off a $100 item saves $20 and leaves a sale price of $80.
Two discounts do not add up
If a store takes 35% off and then gives you a further 10% off with a coupon, the second discount is taken from the already lower price, not from the original. So the total is less than 45% off:
sale price = original x (1 - first discount) x (1 - second discount)
The calculator has an "extra percent off" box for this, and it shows the true total discount.
Adding sales tax
Sales tax is charged on the price after the discount. If you enter a tax rate, the calculator adds it to the sale price to give the total you pay at the register.
A worked example
A jacket costs $59.99. It is 35% off, you have a code for another 10% off, and the sales tax is 8.25%.
| Step | Amount |
|---|---|
| Original price | $59.99 |
| After 35% off ($59.99 x 0.65) | $38.99 |
| After a further 10% off ($38.99 x 0.90) | $35.09 |
| You save | $24.90 (41.5% off in all) |
| Sales tax at 8.25% | $2.90 |
| Total to pay | $37.99 |
Mode 2: find the percent off
If you know the original price and the sale price, the calculator finds the discount:
percent off = (original price - sale price) / original price x 100
For example, a $80 item now costs $60. The saving is $20, and $20 / $80 is 25% off. If the new price is higher than the original, the calculator shows a price increase instead.
Mode 3: find the original price
If you see a sale price and know the discount, you can work back to the price before the sale. The sale price is what is left after the discount, so it is a share of the original:
original price = sale price / (1 - percent off / 100)
For example, $80 after 20% off means the original price was $80 / 0.80 = $100. A common mistake is to add 20% of $80 to get $96, which is wrong, because the 20% was taken from the higher price.
Chart: what you pay compared with the original
The same $100 item at common discounts. The bar shows what you pay:
10% off ████████████████████████████████████ $90 20% off ████████████████████████████████ $80 30% off ████████████████████████████ $70 40% off ████████████████████████ $60 50% off ████████████████████ $50
Quick mental tricks
- 10% off: move the decimal point one place to the left, then subtract.
- 20% off: find 10%, double it, then subtract.
- 25% off: divide by 4, then subtract.
- 50% off: divide by 2.
Good to know
- Check whether a coupon applies to the sale price or to the original price. The calculator assumes it applies to the sale price.
- Some stores round the tax on each item, and others round it on the whole bill, so your receipt may differ by a cent or two.
- A big percentage off a raised "original" price is not always a good deal. Compare with other stores.
This tool gives an estimate for general information only. The price at the register is the price that counts.