How to use this calculator
- Enter the Original price printed on the tag.
- Type the Discount percentage, for example 30 for 30% off.
- If the store takes more off at the register, add it in Extra discount; it is applied after the first one.
- Add your Sales tax rate to see the Final price, then check You save and Total discount.
How a percent-off discount works
A discount of 30% means you pay 70% of the price. So you multiply the price by one minus the discount rate. Tax, if any, is added to the discounted price, not the original, which is why sales tax on a sale item is lower.
Final = Price × (1 − d₁) × (1 − d₂) × (1 + tax)- Price = original price
- d₁ = first discount as a decimal (30% = 0.30)
- d₂ = extra discount as a decimal, applied to the already reduced price
- tax = sales tax rate as a decimal
Example: a $199 jacket with 30% plus 10% off
A $199 jacket is 30% off, and a coupon takes 10% off the sale price, in a place with 8% sales tax. The price before tax is $125.37, tax adds $10.03, and the final price is $135.40. You save $73.63 compared with $199, a total discount of 37%, not 40%.
That gap is the point of stacking: the second percentage applies to a smaller number. Entering a single 37% discount gives the same $135.40 final price.
Another case: 50% off plus 20% off
An $80 item marked 50% off with an extra 20% off costs $32 with no tax, a saving of $48 and a total discount of 60%. Combined percentages are never simply added: 50% and 20% make 60%, and 30% and 10% make 37%. Always compare final prices rather than headline percentages.
How to use the result
Decide whether a deal is worth it by looking at the final price against what you would otherwise pay, not at the size of the percentage. A 70% discount on an inflated list price can still cost more than the everyday price elsewhere.
If you are on the seller side, check what a promotion does to your profit with the profit margin calculator. To reverse a tax-inclusive price and see how much tax is in it, use the sales tax calculator.
Common mistakes
Adding two discounts together is the main error. Others are applying tax to the original price, forgetting that coupons may apply only to full-price items, and ignoring shipping or minimum-spend conditions that change the real cost.
Also ask whether you would buy the item at all without the discount. A saving only helps if the purchase was planned.
Assumptions and limits
The calculator applies the extra discount after the first and then adds one flat tax rate. It does not handle fixed-amount coupons, buy-one-get-one offers, tiered tax, or products taxed at different rates. Some stores apply coupons before or after other discounts in a different order, and the order can change the result for fixed-amount coupons, so check the terms.
Frequently asked questions
How do I calculate 25% off?
Multiply the price by 0.75. A $120 item at 25% off costs $90, so you save $30.
Is 30% plus 10% the same as 40% off?
No. The 10% applies to the already reduced price, so the total is 37% off. Use the extra discount field to check any stack.
Is sales tax charged before or after the discount?
In most places tax is charged on the discounted price. Some jurisdictions treat manufacturer coupons differently, so check local rules.
How do I find the original price from a sale price?
Divide the sale price by one minus the discount rate. If you paid $90 after 25% off, the original was $90 ÷ 0.75 = $120.
How much do I save on a 60% total discount?
You pay 40% of the original price. On $80 that means $32, saving $48.