Discount & Sales Tax Calculator
Find the real final price after discounts and sales tax — and see exactly how much you save.
Final Price
A 30% discount and an 8% sales tax do not cancel out to 22% off. They compound in a specific order, and getting that order wrong is how people end up surprised at the till. This calculator applies them the way a real checkout does.
The order matters
In essentially every jurisdiction, the discount comes off first and tax is calculated on what remains. This is good for you — you are not taxed on money you did not spend. On a $100 item with a 30% discount and 8% tax: the discount brings it to $70, then tax adds $5.60, giving $75.60. If tax were applied first, you would pay $76.32. A small difference on one item; a real one across a full basket. The subtlety is that '30% off plus 8% tax' does not net to 22% off. Percentages of different bases never simply add. Your actual saving is 24.4% off the tax-inclusive price you would otherwise have paid — and the intuition that says 22% is wrong every time. There is one common exception worth knowing: manufacturer coupons are often taxed differently from store discounts, because the store still receives full value from the manufacturer. Some jurisdictions tax the pre-coupon price for exactly that reason.
The formula
Subtotal = Price × Quantity
Discount = Subtotal × Discount%
After Discount = Subtotal − Discount
Tax = After Discount × Tax%
Final Price = After Discount + Tax
Example: $100, 30% off, 8% tax
After discount = $70.00
Tax = $5.60
Final = $75.60Stacked discounts multiply, they do not add. '30% off then an extra 20% off' is not 50% off — it is 0.7 × 0.8 = 0.56, so 44% off. Retailers rely on you not doing that multiplication.
Reading discounts honestly
- 1Stacked percentages multiply. 30% then 20% gives 44% off, not 50%. Every additional discount applies to an already-reduced number, so each one is worth less than it looks.
- 2'Buy one get one free' is 50% off, not 100% off. 'Buy two get one free' is 33% off. Framing sells better than the percentage would.
- 3Compare price per unit, not the discount percentage. A 40% discount on an overpriced item can still cost more than a 10% discount on a fairly priced one.
- 4Check whether the 'original price' was ever real. Many jurisdictions require an item to have sold at the reference price for a set period, and enforcement is patchy. A permanent 50% discount is just the price.
- 5In the US, sales tax is added at the register and varies by city, not just state. In the EU and UK, VAT is already in the displayed price. If you are comparing prices internationally, you are comparing different things.
Frequently asked questions
Is tax calculated before or after the discount?
After, in essentially every jurisdiction. You are taxed on what you actually pay. The exception is some manufacturer coupons, where the retailer still receives full value and certain states tax the pre-coupon price.
Why is 30% off plus 8% tax not 22% off?
Because the percentages apply to different bases. The discount applies to the list price; the tax applies to the discounted price. They never simply add or subtract. Your real saving compared to buying at full price with tax is 30%, not 22%.
How do stacked discounts work?
They multiply. 30% off then 20% off leaves you paying 0.7 × 0.8 = 56% of the original — a 44% discount, not 50%. The second discount only applies to what remains after the first.
What tax rate should I use?
In the US, look up your combined state and local rate — it ranges from 0% to over 10% and varies by city. In the UK it is 20% VAT, already in the shelf price. Most of the EU sits between 19% and 25%, also included in displayed prices.
Does this work for VAT-inclusive prices?
Not directly — this adds tax on top, which is the US model. If your price already includes VAT and you want the pre-tax figure, divide by 1 plus the VAT rate: a £120 price at 20% VAT is £100 before tax.