Scope and assumptions
30% off a single list price; rate 0.30; you pay 70%.
Thirty percent off is retail's most repeated number, and it has an unusually clean mental shortcut: find ten percent, then triple it. On $80 that's $8 × 3 = $24 off, leaving $56 to pay. No calculator, no long division.
The number also has a second name — paying 70% — which is the version that makes the arithmetic faster.
The short answer
30% off means you pay 70% of the price. Multiply by 0.70 and you're finished.
If you need the discount amount instead, it's the price × 0.30. Both come from the same list price; they're the two halves of one split.
Concrete numbers
| List | Discount (30%) | You pay (70%) |
|---|---|---|
| $100 | $30.00 | $70.00 |
| $50 | $15.00 | $35.00 |
| $79.99 | $24.00 | $55.99 |
| $200 | $60.00 | $140.00 |
The ten-percent trick
Move the decimal one place to get 10%, then multiply:
- 10% of $60 = $6
- 30% = $6 × 3 = $18 off
- Or 70% = $6 × 7 = $42 to pay
Two routes, same answer. The second is quicker at the register because it lands directly on the price.
Why 30% is everywhere
Retailers pick it because it sits in a sweet spot: large enough to read as a genuine markdown, small enough to preserve margin, and far from the panic signal of a 50% clearance. It's also easy to communicate — three-tens is intuitive.
| Markdown | You pay | Reads as |
|---|---|---|
| 10% | 90% | token gesture |
| 20% | 80% | mild |
| 30% | 70% | real deal |
| 50% | 50% | clearance |
When 30% is genuinely good
A real 30% off a staple you'd buy anyway is straightforwardly a win. The complication is the base: if the "was" price was raised shortly before the sale, 30% off it can still exceed the normal price. The percentage is only as honest as the number it's measured against.
That's why the useful question isn't "how big is the discount" but "how does this price compare with what this item usually costs?"
Arithmetic Slips on 30% Tags
Paying 30% instead of saving 30%; tripling the ten percent and forgetting to subtract it from the total; using 0.30 when you wanted the sale price; rounding the discount amount before subtracting; and accepting the tag's "was" figure without checking whether it was real.
Related discount guides
A worked example of one rate. For the mental method that builds any rate from 10%, see Percent Off Method, and for the full set of discount formulas start at the hub: Discount Formula.
FAQ
What is 30% off $79.99 exactly? 79.99 × 0.70 = $55.993, which most registers round to $55.99. The discount itself is $24.00.
Is 30% off the same as "buy 3, pay for 2"? No. Getting three for the price of two is 33.3% off, not 30% — you're saving one item out of three.
How do I tell whether a 30% markdown is genuine? Check the "was" price against the item's normal selling price over recent months. If the list price was inflated first, 30% off can still leave you above the usual price. In the US the FTC's guides against deceptive pricing treat such inflated anchors as fake discounts, and the UK's Consumer Protection from Unfair Trading Regulations 2008 enforce the same principle.
What's 30% off if tax is added afterwards? Discount first, then tax on the reduced price. A $100 item at 30% off with 8% tax is $70 × 1.08 = $75.60.
Sources: Khan Academy, Percent word problems; Maths is Fun, Percentages.
Disclaimer: Illustrative. Actual promo terms vary; confirm at checkout. Informational only.
Sources and references
- Khan Academy — Percent word problemshttps://www.khanacademy.org/math
- Maths is Fun — Percentageshttps://www.mathsisfun.com/percentage.html
- FTC — Guides Against Deceptive Pricinghttps://www.ftc.gov/business-guidance/resources/guides-against-deceptive-pricing-practices
Maintenance and corrections
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