Everyday Tools
Discount / Sale Price Calculator
Enter the original price and the discount to see what you save and what you pay, with optional sales tax.
Calculation inputs
Add a second discount if the sale stacks another percentage on top.
Results
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Complete the fields and select Calculate to show results here.
About this calculator
A discount calculator shows the final price of an item after a percentage markdown, how much is saved, and what happens if a second discount or sales tax is added. Shoppers use it to see the real cost of a sale before checking out.
How the calculation works
- Sale price = original price × (1 − discount %)
- A stacked discount applies to the already-reduced price, not the original
- Amount saved = original price − final price
Notes and assumptions
Two stacked 20% discounts are a 36% total reduction, not 40%.
How it works in plain English
The calculator starts by applying the discount percentage to the original price, which reduces the price by that fraction. If a second, stacked discount is entered, it's applied to the already-discounted price rather than the original price, which is how most real-world stacked promotions work. This ordering matters for accuracy: a coupon advertised as 'stacked' promotions almost always compounds this way in stores, rather than adding both percentages together before applying them once.
Once the final discounted price is set, the amount saved is simply the difference between the original price and that final price. The calculator also expresses this as an effective discount percentage, which reflects the true combined savings rather than just adding the two percentages together. This effective percentage is often slightly less than the sum of two discount percentages entered separately, because the second discount is calculated on a smaller base amount than the first one was.
If sales tax applies, it's calculated on the discounted price rather than the original price, matching how tax is typically charged at checkout after any promotional discount has already been applied. This gives a realistic final total that a shopper would actually pay. Entering a 0% tax rate simply returns the discounted price unchanged, which is useful for comparing states or situations where no sales tax applies.
The formula
- Price after first discount = original price x (1 - discount % / 100)
- Price after second discount = previous price x (1 - extra % / 100)
- Amount saved = original price - final price
- Price with tax = final price x (1 + tax % / 100)
Worked example
A $120 item is marked 30% off. The price after the first discount is 120 x (1 - 0.30) = $84.00. If sales tax of 8% applies, the final total is 84.00 x 1.08 = $90.72. The amount saved compared to the original price is 120 - 84 = $36.00, an effective discount of 30% before tax. Two stacked discounts, such as 20% and 20%, would instead combine to a 36% total reduction, not 40%, since the second discount applies to the already-reduced price. Applying that 36% combined reduction to the same $120 item would leave a final price of 120 x 0.64 = $76.80, noticeably lower than the $84.00 result from the single 30% discount used above.
Frequently asked questions
Why don't two 20% discounts add up to 40% off?
The second discount is applied to the price after the first discount, not to the original price. Taking 20% off, then another 20% off that smaller amount, leaves you paying 0.8 x 0.8 = 64% of the original price, a 36% total reduction rather than 40%.
Is sales tax calculated before or after the discount?
This calculator applies sales tax to the discounted price, which reflects how most retailers charge tax at checkout, after any coupon or markdown has already been subtracted from the listed price. This matters because calculating tax on the original price instead would produce a higher total than what most stores actually charge, since the discount is meant to reduce the taxable amount as well as the sticker price.
What does effective discount percentage mean?
It's the actual overall percentage saved compared to the original price, accounting for any stacked discounts. It can differ from simply adding two discount percentages together, since stacked discounts compound rather than add. For a single discount, the effective percentage simply equals the discount entered, but once a second discount is stacked on top, the combined effective percentage will always be a little less than adding the two numbers directly.
Can I use this for a discount amount in dollars instead of a percentage?
This tool works from percentages. To use a flat dollar discount, divide that dollar amount by the original price and multiply by 100 to get the equivalent discount percentage before entering it. For example, a $15 discount on a $75 item is equivalent to a 20% discount, since 15 divided by 75 times 100 equals 20, and entering 20% into the calculator would produce the same final price.
Does the calculator handle discounts over 100%?
A discount at or above 100% would produce a final price of zero or a negative number, which isn't meaningful for a sale price. Discount percentages should stay below 100% for a realistic result. In practice, no real discount exceeds 100%, since that would mean a retailer paying a customer to take an item, so any input at or beyond that level should be treated as a data-entry error rather than a valid promotion.