The basic calculation
To take 20% off a price of 100, calculate the discount amount as 100 × 0.20 = 20. Subtract that amount from the original price to get a discounted price of 80. The calculator shows both the saving and the amount left to pay.
The original price is the baseline. If you apply another percentage later, that second percentage is usually taken from the already reduced price, not the starting price.
Discounts are not the same as final cost
- Sales tax or VAT may be added after the discount, depending on the transaction.
- Shipping, service fees or minimum-order rules may be separate.
- A coupon may have a cap, expiry date or product exclusion.
- A displayed reference price may not be the price that applies to every buyer.
Compare offers using the same basis
- Record the original price and discount percentage.
- Calculate the discount amount and sale price.
- Add any tax, shipping or mandatory fees that apply.
- Compare the final payable amounts, not only the advertised percentages.
Check the result
For a shopping decision, keep the retailer’s terms and the date of the offer. For business pricing, confirm whether the discount is calculated before or after tax and whether the stated price is per item, pack or subscription period.
Common questions
What is 20% off 100?
The discount is 20 and the price after the discount is 80, before any additional tax or fees.
Are two 20% discounts the same as 40% off?
Usually no. Applying 20% and then another 20% leaves 64% of the original price, which is a total reduction of 36%.
Does the calculator know a shop’s promotion rules?
No. Enter the terms that apply to your offer and check the retailer’s conditions separately.