What to enter
- What do you want to find?
- Choose “The final price after a discount” to price a sale, or “The percent off from two prices” to find out how big a reduction is.
- Original price
- The regular price before any discount. Use the price actually charged before the sale, not a “compare at” price you cannot verify.
- Discount
- The percentage taken off the original price.
- Extra discount taken after the first (optional)
- A second percentage, such as an additional “take 10% off” coupon. It applies to the price after the first discount, not to the original price.
- Sales tax (optional)
- The tax rate to add after discounts. Leave it at zero if you only want the pre-tax price.
- Sale price
- In the reverse mode, the discounted price you see.
How to read your results
In the sale mode, the headline is the final price you pay, including tax if you entered a rate. The table shows the discount in dollars, the price after discount, the tax and the amount you save. When you enter a second discount, two extra lines show the second discount in dollars and the combined discount, which is the single percentage that the two discounts add up to. In the reverse mode, the result is the percentage off the original price, the amount saved, and the share of the original price you actually pay.
The formulas
Price after second discount = that price × (1 − d₂)
Final price = discounted price × (1 + tax rate)d₁, d₂ and the tax rate are written as decimals: 20% = 0.20.
Percent off from two prices = (original − sale) ÷ original × 100
Because each discount applies to the price left after the previous one, the order does not change the result, but the percentages never simply add up.
Worked example
A $100 item at 20% off
The discount is $20.00, the price after discount is $80.00 and, with no tax, the final price is $80.00.
Adding a coupon and tax. Take an extra 10% off the $80 sale price and the price falls to $72.00, a combined discount of 28%, not 30%. With 8% sales tax added, the final price is $77.76.
The stacking trap. Two discounts of 50% and 20% sound like 70% off, but they combine to 60% off: $100 becomes $40.00.
Reverse mode. An item that was $129.99 and is now $89.99 has been reduced by $40.00, which is 30.77% off the original price.
Reading sales and comparing offers
A larger percentage is not always a better deal. Compare the final prices, not the discounts: 30% off a high starting price may cost more than 15% off a lower one. When a coupon “stacks” with a sale, check the terms, since many coupons apply only to the regular price or exclude sale items. Shipping fees, handling fees and taxes are separate from the discount, so compare the total you will pay.
Be wary of inflated “original” prices. Federal Trade Commission guidance says that a former price used in an advertisement should be a genuine price at which the item was actually offered to the public on a regular basis for a reasonable period. When the original price is doubtful, compare the sale price with what other stores charge instead.
Percentage discounts also change the price you use to calculate sales tax, and in most places tax is charged on the discounted price. Store coupons usually reduce the taxable amount, while some manufacturer coupons do not, depending on the state. The sales tax calculator can work out the tax on the final price, and the percentage calculator covers other percentage questions.
Assumptions and limits
The calculator handles percentage discounts only. It does not model buy-one-get-one offers, fixed-dollar coupons, tiered quantity discounts, rebates or shipping. It assumes tax is charged on the discounted price at the single rate you enter, which is the usual case but is not universal.
Frequently asked questions
How do I calculate a discount?
Multiply the original price by the discount percentage as a decimal, and subtract the result from the original price. Twenty percent off $100 is $100 − $20 = $80.
Why is 20% off plus 10% off not 30% off?
Because the second discount applies to the price already reduced by the first. Together they equal 28% off.
Is sales tax charged before or after the discount?
Usually after, on the discounted price. Some coupons and rebates are treated differently, so check the receipt or local rules.
How do I find the percent off from two prices?
Subtract the sale price from the original price, divide by the original price and multiply by 100. Use the reverse mode to do it automatically.
What if the sale price is higher than the original?
The reverse mode reports a price increase instead of a discount.