Discount Calculator: Percent Off, Sale Price and Savings

Worked examples

$80 item at 25% off

25% of $80 is $20.00, so you save $20.00 and pay $60.00.

Work backward from a sale price

You paid $60.00 after 25% off. The original price was $60 ÷ (1 − 0.25) = $80.00, a $20.00 saving.

Stacked 20% then 10% on $100

$100 drops to $80.00 after 20% off, then to $72.00 after another 10% off. That is an effective 28% discount, not 30%.

Add sales tax

A $60.00 sale price with 8% sales tax comes to $64.80 at the register.

How the discount calculator works

A discount is a percentage taken off a price. Every calculation here comes down to one idea: turn the percentage into a decimal, then multiply. The tool has three modes (percent off, finding the original price, and stacking two discounts), plus an optional sales tax field.

Percent off: sale price and savings

This is the everyday case. You know the original price and the discount, and you want the sale price and how much you save:

Amount saved = original price × (discount % ÷ 100)
Sale price = original price − amount saved

Take an $80 jacket at 25% off. The saving is 80 × 25/100 = $20.00, so the sale price is 80 − 20 = $60.00. A quick shortcut: paying “25% off” is the same as paying 75% of the price, so 80 × 0.75 = $60.00 gets you there in one step.

Reversing it: finding the original price

Sometimes you have the sale price and the discount, and you want to know the original (for example, to check how good a deal really was). Because the sale price is the original times the remaining fraction, you divide to reverse it:

Original price = sale price ÷ (1 − discount % ÷ 100)

If you paid $60.00 after a 25% discount, the original was 60 ÷ (1 − 0.25) = 60 ÷ 0.75 = $80.00. This works for any discount below 100%. A 100% discount makes the item free, and dividing by zero has no answer, so the calculator asks for a discount under 100% in that mode.

Why two stacked discounts compound instead of add

Store promotions often layer offers, like “20% off, plus an extra 10% at checkout.” It is tempting to add them to 30%, but discounts do not add. The second discount applies to the already-reduced price, so it compounds:

Final price = original × (1 − first % ÷ 100) × (1 − second % ÷ 100)

Start with a $100 order. After 20% off it is 100 × 0.80 = $80.00. The extra 10% then comes off that $80, not the original $100: 80 × 0.90 = $72.00. You saved $28.00, which is an effective 28% discount, not 30%. The gap grows as the percentages get larger, which is why “stacked” coupons rarely reach the sum of their labels.

Adding sales tax

Discounts are applied before tax, and tax is charged on the price you actually pay. So work out the sale price first, then add tax on top:

Total with tax = sale price × (1 + tax % ÷ 100)

A $60.00 sale price with 8% sales tax comes to 60 × 1.08 = $64.80. The calculator shows both the pre-tax sale price and the post-tax total so you can see the tax portion clearly. Leave the tax field at 0 to skip it.

A note on accuracy

These figures are estimates for planning and comparing deals. Real receipts can differ because of rounding at the register, tax rules that vary by location and item, and promotions that exclude certain products. Check the store’s terms before assuming a stacked coupon or a specific tax rate applies.

Frequently asked questions

How do I calculate a percent off?

Multiply the original price by the discount percentage divided by 100 to get the amount saved, then subtract that from the price. For $80 at 25% off: 80 × 25/100 = $20.00 saved, so the sale price is 80 − 20 = $60.00.

How do I find the original price from a sale price?

Divide the price you paid by 1 minus the discount as a decimal. If you paid $60.00 after a 25% discount, the original price was 60 ÷ (1 − 0.25) = 60 ÷ 0.75 = $80.00. This only works for discounts below 100%, because a 100% discount makes the item free and leaves no way to recover the original.

Do stacked discounts add up to one big discount?

No. Two discounts compound rather than sum, because the second one applies to the already-reduced price. A 20% discount followed by a 10% discount is not 30% off. On $100 you get $72.00, which is 28% off, since the 10% comes off $80 (not the full $100).

How do I add sales tax to a discounted price?

Work out the sale price first, then multiply it by 1 plus the tax rate as a decimal. A $60.00 sale price with 8% tax is 60 × 1.08 = $64.80. Tax is charged on what you actually pay, so applying the discount before the tax is correct.

How do I compare two deals?

Convert both to a final price for the same item and compare those, not the headline percentages. A flat $25 off a $100 item beats 20% off ($20 saved), and a single 28% coupon beats a 20% plus 10% stack (also 28%) only if it applies to the same base. The final price is the number that matters.