Discount Calculator
Enter an original price and a percent or dollar discount to get the final price and savings, work backward from a sale price to find the discount rate, or stack two discounts correctly — a $100 item at 20% off then 10% off comes to $72, an effective 28% off, not the 30% you'd get by adding the percentages. Add an optional sales tax (GST/HST/PST) rate, applied to the discounted price.
$40.00
Final price
Original $50.00 at 20% off
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Sales tax is always calculated on the price after every discount, never on the original price. How we calculate →
How do discounts work? (the percent-off formula)
A percentage discount reduces the original price by a share of itself: Final price = Original price × (1 − discount% ÷ 100). A $50.00 item at 20% off: discount amount = $50.00 × 20% = $10.00, so the final price is $50.00 − $10.00 = $40.00.
A dollar-amount discount ("$15 off") works even more directly: subtract the flat amount from the original price. Switch modes above to go either direction — percent off, dollar amount off, or figure out what percentage a sale price actually represents.
Stacked discounts: why 20% off + 10% off is NOT 30% off
The single most common discount mistake is adding two percentages together. A $100.00 item marked 20% off, then an extra 10% off at checkout, does not come to 30% off ($70.00). The second discount applies to the already-discounted price, not the original: after the first 20% off, the price is $80.00; take 10% off THAT, and the final price is $72.00.
That's an effective discount of 28%, not the naively-added 30% — you pay $2.00 more than a true 30%-off sale would charge on this $100.00 item. The stacking mode above runs this calculation for any two percentages, so you can see the real total before you check out.
Working backward: finding the original price (or the discount rate) from a sale price
Sometimes you know the before and after prices and want the discount rate itself: Discount % = (Original − Final) ÷ Original × 100. An item that dropped from $100.00 to $75.00 saved you $25.00, which is 25% off — useful for checking whether an advertised "up to 50% off" sale actually applied that rate to the item you bought.
Does sales tax apply before or after the discount?
In the US and Canada, retailers calculate sales tax on the price you actually pay — after the discount is applied, not on the original sticker price. On a $80.00 discounted price with an 8% sales tax rate: tax = $80.00 × 8% = $6.40, for a total of $86.40 at checkout.
This matters for stacked discounts too: tax is calculated once, on the final discounted price after every markdown has been applied — never on the original price, and never taxed separately at each discount step. The sales tax field above is optional and always applies to the final, post-discount price.
Frequently asked questions
How do I calculate a discount?
Multiply the original price by the discount percentage, then subtract that amount from the original price. On a $50.00 item at 20% off, the discount is $10.00, so you pay $40.00.
What is 20% off $50?
20% off $50.00 is $40.00. The discount amount is $50.00 × 20% = $10.00, and $50.00 − $10.00 = $40.00.
How do I figure out the original price before a discount?
If you know the discount percentage and the final price, original price = final price ÷ (1 − discount% ÷ 100). If instead you know both the original and final price and want the rate itself, use (Original − Final) ÷ Original × 100 — a drop from $100.00 to $75.00 is a 25% discount.
Is 20% off then 10% off the same as 30% off?
No. On a $100.00 item, 20% off then 10% off brings the price to $72.00 (an effective 28% off), while a straight 30% off would bring it to $70.00. Stacked percentage discounts are always smaller in total than simply adding the percentages, because the second discount is taken off a smaller, already-reduced price.
Does sales tax apply before or after a discount?
After. Retailers in the US and Canada calculate sales tax on the price actually paid, once every discount has already been subtracted. On an $80.00 post-discount price with 8% tax, you pay $6.40 in tax for a total of $86.40 — not tax on the original, higher sticker price.
What's the difference between percent off and dollar amount off?
Percent off scales with the price ($15 off a $30 item is a bigger relative discount than $15 off a $150 item), while a flat dollar amount off is the same saving regardless of price. Both modes are available above — use whichever matches how the sale is advertised.
How much do I save with a stacked discount?
Apply the first percentage to the original price, then apply the second percentage to the already-discounted result — never to the original price twice. Use the stacking mode above to see the exact dollar total and the real effective percentage for any two discounts.
Researched & verified by the Calcuris Data & Research Team. How we build and check our tools →