Discount Calculator

This works out what something actually costs once a discount is applied, and what you save. It handles a percentage off, a fixed amount off, two discounts stacked one after the other, and sales tax on the result. Enter the original price, pick the discount type, and the answer updates as you type.

The two common kinds of discount

The word discount covers any reduction in price, but almost everything you meet in a shop is one of two forms: a percentage off, or a fixed amount off.

Percent off

A percentage off takes a share of the original price away. If something costs $45 with 10% off, work out 10% of $45 and subtract it:

10% of $45 = 0.10 × 45 = $4.50

$45 − $4.50 = $40.50

There is a quicker route to the same answer. Taking 10% off leaves 90%, so multiply straight through:

90% of $45 = 0.90 × 45 = $40.50

One step instead of two, and it is the version worth learning because it extends cleanly to stacked discounts. Either way you save 10%, or $4.50.

Fixed amount off

A fixed amount is simpler: subtract it from the price. A service normally costing $95 with a $20 coupon comes to:

$95 − $20 = $75

You save the $20 whatever the price is, which is the key difference between the two forms. A percentage scales with the price and a fixed amount does not, so a $20 coupon is a 40% discount on a $50 item and a 4% discount on a $500 one. When a shop offers you a choice between "$20 off" and "20% off," the crossover is at $100: below that the fixed amount wins, above it the percentage does.

Stacked discounts

This is where people are most often caught out. A shop offering 20% off, then a further 15% off the reduced price, is not offering 35% off.

Take $100. The first discount removes $20 and leaves $80. The second is 15% of $80, not of $100, so it removes $12 rather than $15. The final price is $68, and the combined discount is 32%, not 35%. Turn on the second discount above and the breakdown table shows each step.

The shortcut is to multiply what remains: 0.80 × 0.85 = 0.68, so 32% off. The order does not matter for two percentages, since multiplication commutes, and you land on $68 either way. Order does matter when one of them is a fixed amount: taking $20 off before a 15% discount gives $68, while taking the 15% first gives $65. Retailers generally apply percentages before fixed-value coupons, though it varies, so read which is applied first when the difference matters.

The same arithmetic explains a claim you sometimes see: three stacked 10% discounts sound like 30% but come to 27.1%, because each one is smaller than the last.

Where sales tax fits

In the United States, sales tax is charged on the discounted price, not the original one, so a discount reduces the tax as well. A $100 item with 20% off in a state charging 8% tax comes to $80 plus $6.40, or $86.40 total, rather than $80 plus the $8 that would have been due on the full price.

There is one wrinkle worth knowing. Store coupons, funded by the retailer, reduce the taxable amount as above. Manufacturer coupons, where the shop is reimbursed by the brand, are treated in many states as though the shop received full price, so tax is charged on the pre-coupon amount. This is why two identical-looking coupons can produce different totals at the till. Our Sales Tax Calculator handles the tax side in more detail.

Reading a discount honestly

The arithmetic is easy. Judging whether a discount is good is the harder part, and a few habits help.

Compare against the price you would otherwise pay, not the sticker. A "was $200, now $120" claim only means something if anything was ever sold at $200. Reference pricing rules exist in many jurisdictions precisely because inflated original prices are a recurring problem, and the FTC treats a former price as deceptive unless it was a genuine, recent, substantial-volume price.

Watch percentage-off framing on large items. 10% off a $1,200 sofa saves more in cash than 50% off a $60 jacket, but the second feels like the bigger win. Comparing the dollars saved, which the panel above shows, corrects for that.

A discount on something you did not want is not a saving. Spending $68 instead of $100 saves nothing if you would otherwise have spent nothing. The saving is real only against a purchase you were going to make anyway.

Check the unit price on multi-buys. "Three for $10" is only a deal if the single price is above $3.33, and it frequently is not.

Know the normal price before the sale starts. The most useful habit is tracking what an item usually costs over a few months, because most categories run on predictable cycles. Furniture, mattresses, and appliances are discounted around public holidays; clothing is marked down at the end of each season; electronics fall when a replacement model is announced. A 30% discount during a sale that runs eleven months of the year is closer to the real price than the sticker is.

Discounts that are not what they appear

• Buy one get one free is a 50% discount if you wanted two, and a 0% discount if you wanted one. Buy one get one half price is 25% off two items, not 50% off.
• "Up to 70% off" describes the best item in the sale, usually in one remaining size. The typical reduction is far lower.
• Free shipping thresholds regularly cost more than the shipping. Adding a $15 item to avoid a $6 delivery charge spends $9 you did not need to spend.
• Percentage off before or after other adjustments. A discount applied before a fee or delivery charge saves less than one applied to the full total.
• Store credit rather than money off. "Spend $100, get $20 back" is a coupon for a future purchase, which is a discount on your next spend rather than this one.

Working discounts out in your head

A few shortcuts cover most real cases without a calculator.

For 10%, move the decimal point one place: 10% of $45 is $4.50. For 20%, do that and double it. For 5%, do it and halve it. For 15%, take 10% and add half of it again, so $4.50 plus $2.25 is $6.75.

For 25%, quarter the price. For 33%, take a third. For 50%, halve it. And a trick that surprises people: percentages are reversible, so 8% of 50 equals 50% of 8, which is 4. When one side is awkward, flip it.

To go the other way and find the original price from a sale price, divide rather than multiply. Something on sale at $68 after 32% off was $68 ÷ 0.68 = $100. Adding 32% back to $68 gives $89.76, which is a different and wrong answer, and it is the most common mistake with reverse percentages. The Percent Calculator covers the general case.

Reading the result

The panel shows the final price, what you save in dollars, and the total percentage off, which is the figure to quote when stacking discounts since it accounts for the compounding. The second chart puts your price against the same item at 10% through 70% off, which is a quick sense of where a given deal actually sits.