About the Percent Off Calculator
A percent off calculator computes the price of an item after a percentage discount. Behind the simple math is one of the most common consumer-decision tools: "how much will I actually pay?" It also shows you how percent discounts on already-discounted items combine, why "30% off plus 20% off" is not 50% off, and how taxes and additional fees interact with the discount.
The math, plainly
Final price = original × (1 − discount). For a $80 item at 25% off: $80 × 0.75 = $60. The discount amount is original × discount: $80 × 0.25 = $20. These are equivalent computations expressed two ways.
Working backwards: if you paid $60 for an item that was 25% off, the original price was $60 / 0.75 = $80. The discount amount was $80 − $60 = $20. The asymmetry — going from original to sale uses multiplication, going from sale to original uses division — is the source of many "why doesn't 25% off cancel by adding 25%?" confusions.
Why 25% off then 25% off ≠ 50% off
Stacking discounts compounds rather than adds. A 25% discount followed by another 25% discount: $100 × 0.75 = $75, then $75 × 0.75 = $56.25. Total discount: 43.75%, not 50%. This is the classic "clearance plus extra discount" arithmetic that retailers rely on for headline figures that exceed the actual savings.
The combined-discount formula: total off = 1 − (1 − d1)(1 − d2). For three stacked 20% discounts: 1 − 0.8³ = 48.8%. For the discount to actually be 50%, you'd need either a single 50% discount or specific combinations like 20% + 37.5% off the reduced price.
Sales tax interactions
Sales tax is applied to the post-discount price in most jurisdictions. A $100 item at 25% off in a 7% sales tax area: $75 × 1.07 = $80.25 final price. The tax effectively makes the discount slightly less valuable in absolute dollars (you save $25 on price but only $23.25 on total), though the percentage savings is unchanged.
Some discounts (manufacturer rebates, store credits) are sometimes treated differently from instant coupons for tax purposes — a manufacturer rebate may apply after tax in some states. Read the receipt's tax line if it matters; cumulative effects across many purchases can be meaningful.
When the headline discount isn't the real discount
"Up to 70% off" usually means a small subset of items hit that ceiling. "50% off MSRP" assumes the full MSRP is the relevant baseline — sometimes it isn't, because the item rarely sold at MSRP. Camelcamelcamel-style price-history tools have shown that many products spend most of their lifetime at "sale" prices, with the MSRP serving as an anchor that exists more for psychological framing than as a real reference.
The honest comparison is the actual price you'd pay against the actual price you'd pay at competitors or in recent months. Discount percentages are useful within a single retailer's pricing; across retailers and over time, dollar prices are the cleaner basis for decisions.
Formula
- original = Pre-discount price
- discount % = Discount expressed as a decimal (25% = 0.25)
- Discount amount = original × discount %
Worked examples
$120 at 30% off
Discount: $120 × 0.30 = $36. Final price: $120 × 0.70 = $84. Or equivalently: $120 − $36 = $84.
Stacked 30% + 20%
$120 × 0.70 = $84 (after first discount). $84 × 0.80 = $67.20 (after second). Total saved: $52.80, or 44% off the original — not 50%.
Discount with sales tax
$200 item, 25% off, 8% sales tax. Discounted price: $150. Tax: $12. Total at register: $162. Compared to no-discount: $216. Real savings: $54.
Frequently asked questions
How do I calculate a percent discount?
Multiply the original price by the discount expressed as a decimal to find the savings, or by (1 − discount) to find the final price. For 25% off $80: savings = $80 × 0.25 = $20; final = $80 × 0.75 = $60.
Why isn't 25% + 25% off the same as 50% off?
Because the second 25% applies to the already-discounted price, not the original. $100 × 0.75 = $75; $75 × 0.75 = $56.25 — that's 43.75% off, not 50%. Stacked discounts compound (multiply), not add.
How do I find the original price from the sale price?
Divide the sale price by (1 − discount). If you paid $60 for an item that was 25% off, the original was $60 / 0.75 = $80. This is the reverse of applying a discount and is the one most people get wrong.
Is sales tax applied before or after the discount?
Almost universally after the discount, in U.S. retail. The tax is calculated on the price you actually pay, not the original sticker price. A few exceptions exist for certain manufacturer rebates that some states treat as applying to a price that has already been taxed.
How do I compare two discounts?
Compute the final price for each and compare in dollars. "25% off" and "$30 off" can favor different items depending on the original price. For an $80 item: 25% off = $20 off, so $30 off wins. For a $200 item: 25% off = $50 off, so the percent discount wins.
What is markup vs. markdown?
Markup is the percentage added to a cost to set the selling price; markdown is the percentage subtracted from a price to mark it down for sale. They use the same arithmetic but the base is different — markup uses cost as the base, markdown uses the original selling price.
Related calculators
Concepts
Sources & methodology
- Federal Trade Commission — Pricing and discount disclosure guidelines — source