How to calculate a discount
Multiply the original price by the discount percentage and divide by 100 to find the amount off. Subtract that from the original price for the sale price. Add an optional sales tax percentage and the calculator applies it to the discounted price to show what you'll actually pay at checkout.
The formulas
Amount off = Price × disc% ÷ 100 · Sale = Price − Off · Final = Sale × (1 + tax%)
Worked example
$80 at 25% off:
- Amount off: $80 × 25 ÷ 100 = $20
- Sale price: $60
- With 8% sales tax: $60 × 1.08 = $64.80 at checkout
Why stacked discounts surprise people
Two discounts don't simply add up. A 20% then 10% coupon isn't 30% off — the 10% applies to the already-reduced price, so you pay 0.80 × 0.90 = 0.72 of the original, i.e. 28% off, not 30%.
Common mistakes to avoid
Adding stacked discount percentages together. Applying tax before the discount instead of after. Treating any percentage off as a "deal" regardless of whether you needed the item. Forgetting shipping, which can erase a small discount.
Frequently asked questions
What is 25% off $80?
25% of 80 is 20, so the sale price is $60.
How do I stack two discounts?
Apply them one at a time. 20% then 10% is 28% off, not 30%, because the second applies to the reduced price.
How do I add tax to a sale price?
Multiply the discounted price by (1 + tax rate). Use the optional tax field.
How do I find the percent off from two prices?
(Original − Sale) ÷ Original × 100. From $80 to $60 = 25% off.
Is a discount always worth it?
Only if you needed the item — a percentage off something you wouldn't have bought still costs money.
Is my data saved?
No. Everything runs in your browser; nothing is uploaded.