How Discounts Actually Work
Every discount comes down to one of two things: a slice of the price expressed as a percentage, or a flat amount knocked off. Percentages scale with the price, so 20% off saves you more on a $500 item than on a $50 one. Fixed amounts do the opposite — a $20 coupon is a huge deal on a $40 purchase and barely noticeable on a $400 one.
That difference is why converting between the two is so useful. A $15 coupon on a $60 item is exactly 25% off, which instantly tells you whether it beats the 20%-off sale running next to it. Switching the discount type to a dollar amount does that conversion automatically, and the table under the calculator shows the same price at a dozen common discount levels so you can compare offers at a glance.
Every Formula This Calculator Uses
Why Stacked Discounts Are Never What They Look Like
This is where most people lose money in their heads. A sign reading "20% off, plus an extra 10% off at the register" looks like 30%. It is not. The second discount applies to the already-reduced price, so on a $100 item you go to $80, then take 10% off that — $8, not $10 — landing at $72. Your real saving is 28%.
The gap widens as you add more layers. Three discounts of 30%, 20% and 10% sound like 60% off; run them properly and you pay $100.80 on a $200 item, which is 49.6%. The Extra % Off tab spells out each step and then tells you what the combined discount really works out to, so you can compare it honestly against a single-percentage offer elsewhere.
One genuinely useful quirk: the order of percentage discounts does not matter. Taking 20% then 10% gives exactly the same result as 10% then 20%, because you are multiplying the same two factors. Order does matter when a fixed-dollar coupon is involved — having the dollars come off before a percentage leaves you paying less than the other way round, which is worth knowing at the register.
Working Backwards From a Sale Price
Two reverse questions come up constantly. The first is "what percentage off is this?" — you can see the original and sale price on the tag and want to know if the deal is any good. Subtract, divide by the original, multiply by 100.
The second is "what was this before the sale?" — useful when a listing only shows the discounted price and the claimed percentage. Here you divide rather than multiply: a $90 item at 25% off means you are paying 75% of the original, so the original was $90 ÷ 0.75 = $120. A surprisingly common error is to add the percentage back to the sale price instead, which gives $112.50 and is wrong. The main Discount section handles every direction: fill in any two boxes and it works out the rest.
BOGO, 3-for-2 and Other Multi-Buy Offers
Multi-buy deals hide their real discount behind the headline. Buy one get one free is 50% off — but only across two items, and only if you genuinely wanted two. Buy one get one half off is far weaker: you pay $50 plus $25 for two $50 items, so $75 for $100 of goods, which is 25% off, not 50%.
Three-for-two works out to 33.3% off. Buy three get one free is 25%. The pattern is simple once you see it: your saving is the value of the free items divided by the value of everything you take home, not divided by what you paid. The Buy One Get One tab computes this along with the average price per item, which is the number worth comparing against a competitor's straight percentage sale.
The honest caveat on all of these: a multi-buy discount only saves money on units you actually need. Two of something at 50% off is not cheaper than one at full price if the second one sits unused.
Where Sales Tax Fits In
In the United States, sales tax is applied to the discounted price rather than the original, which means a real discount quietly saves you tax as well. On a $120 item at 25% off in a state with 8.25% tax, you pay tax on $90, not $120 — so the total is $97.43 instead of the $107.93 you would have paid without the sale.
There is a wrinkle worth knowing. Store coupons generally reduce the taxable amount, but manufacturer coupons sometimes do not, because the retailer is reimbursed for that amount and the state still treats it as part of the sale price. This varies by state, so the tax figure this calculator produces is a close estimate rather than a guarantee. Enter your local combined state and local rate for the most accurate result.
Spotting a Discount That Isn’t Really a Discount
A percentage is only meaningful relative to the price it is measured against, and that reference price is chosen by the seller. An item permanently listed at $200 and permanently "40% off" at $120 has a real price of $120. The discount is presentation.
Two practical habits help. Check what the item has actually sold for recently rather than what the sticker claims it was worth — price history browser extensions and marketplace listings make this easy. And judge the discount against the category norm: 20% off clothing at the end of a season is ordinary, while 20% off a current-model appliance is genuinely unusual. The percentage on the sign tells you about the seller's pricing strategy; the comparison against real recent prices tells you whether you are getting a deal.
A Worked Example
You are looking at a $120 jacket. The store advertises 25% off, and you also have a 10% email coupon that stacks. Sales tax where you live is 8.25%.
The first discount takes $30 off, leaving $90. The second takes 10% of $90 — that is $9, not $12 — leaving $81. Your combined discount is 32.5%, not the 35% the two signs suggest. Tax is charged on $81, adding $6.68, so you hand over $87.68.
Compare that against a competitor selling the same jacket at a flat $85 with no coupon. Before tax, the stacked deal wins by $4. After tax, it still wins — $87.68 against $92.01. Without running the numbers, the "25% plus 10%" framing makes it hard to see that the margin is only a few dollars rather than the double-digit saving it appears to be.
Frequently Asked Questions
How do I calculate a percentage discount?
Multiply the original price by the discount percentage divided by 100 to get the amount you save, then subtract that from the original price. A quicker shortcut is to multiply the price by what you still pay: for 25% off, you pay 75%, so $80 × 0.75 = $60. Both routes give the same answer.
Is 20% off plus an extra 10% off the same as 30% off?
No, and this is the single most common discount mistake. The second discount comes off the already-reduced price, not the original. On a $100 item, 20% off leaves $80, and 10% off that is $72 — a true saving of 28%, not 30%. Stacked discounts always work out to less than the two percentages added together.
How do I find the original price from a sale price?
Divide the sale price by one minus the discount as a decimal. If you paid $80 after 20% off, the original was $80 ÷ 0.80 = $100. The main Discount section does this for you — enter the final price and the discount percentage and leave the original price at zero.
How do I work out what percentage discount I got?
Subtract the sale price from the original price, divide the result by the original price, then multiply by 100. An item marked down from $80 to $60 saves you $20, and $20 ÷ $80 = 0.25, so that is 25% off. This also lets you convert a dollars-off coupon into a percentage so you can compare it against a percentage sale.
Is sales tax charged before or after a discount?
In the United States, sales tax is normally calculated on the discounted price, not the original one — so a genuine discount lowers your tax bill too. Retailer coupons reduce the taxable amount in most states, though manufacturer coupons sometimes do not because the store is reimbursed for them. Rules vary by state, so treat the tax figure here as a close estimate.
Is buy one get one free the same as 50% off?
Only if you actually want both items. Buy one get one free on a $50 product means paying $50 for two, which works out to 50% off per item. But you have spent $50, not $25, and you have to want the second one for the saving to be real. Buy one get one half off is a smaller deal than it sounds: it is 25% off across the two items, not 50%.
Can you stack a coupon on top of a sale price?
It depends entirely on the retailer's policy — many allow one manufacturer coupon plus one store coupon, while others exclude already-reduced clearance items. When stacking is allowed, the order usually does not change your final price, because multiplying by two discount factors gives the same result either way. The exception is a fixed-dollar coupon combined with a percentage: taking the dollars off first, then the percentage, leaves you paying less.
What counts as a good discount percentage?
It depends on the category rather than the number itself. Clothing and seasonal goods routinely hit 40–60% off at end of season, so a 20% clothing sale is unremarkable. Electronics and appliances move in much narrower bands, where 10–15% off can be a genuinely strong price. The more useful check is comparing the sale price against what the item has actually sold for recently, rather than against the sticker price the discount is measured from.
This calculator provides estimates for general informational purposes only. Sales tax treatment of coupons and discounts varies by state and by whether a coupon is issued by the store or the manufacturer — the total shown here is an estimate, and your receipt is the authority.