A big red sale sign does not always mean a big saving. Sometimes the price was quietly raised first, sometimes two smaller discounts are dressed up as one large one, and sometimes a deal that never ends is simply the normal price. The safest habit is simple: work out the numbers yourself before you buy.
Disclosure: I made All Done, the free tools site linked below.
The basic formula, without the jargon
Every discount comes down to three numbers: the original price, the price you actually pay, and the percentage taken off. If you know the original price and the percentage, multiply the original price by that percentage to find the saving, then subtract it from the original price.
For example, a $60 coat at 25% off saves $15, so you pay $45. Going the other way, if something falls from $80 to $60, the $20 saving is 25% of $80.
Why 20% plus 10% is not 30%
Stacked offers are a common trap. An extra 10% is usually taken from the already-reduced price, not from the original price. So 20% off, followed by 10% off the sale price, gives a total saving of 28%, not 30%. Always apply each discount in turn.
Working backwards to check a claim
If you only see the sale price and the percentage, divide the sale price by what remains after the discount. For instance, a $70 item sold at 30% off means you paid 70% of the original price, so the original was $100. Use the same check on a crossed-out price: if the store's claimed original price does not match the sale price and percentage, the deal is weaker than advertised.
Seven tricks to watch for
- Inflated "was" prices that were raised just before the sale.
- Endless sales that never actually end.
- Countdown timers that reset instead of expiring.
- Suggested retail prices no shop ever charged.
- Loss leaders: one bargain item that fills the rest of your cart.
- Bundle deals where the per-item price is no better.
- Limited-stock warnings that stay on screen for every visitor.
Quick mental math in the aisle
Ten percent is easy: just move the decimal point one place. Ten percent of $80 is $8. For 20% off, multiply the price by 0.8, or find 20% and subtract it. And do not forget tax and delivery: a discount can look smaller once those are added.
Check it before you buy
Do not trust the tag blindly. Punch the numbers into the free Discount Calculator to see the true percentage and final price.
The full guide is on All Done at https://all-done.xyz/blog/discount-calculation-guide-spot-real-deals — this post is a cross-post of that guide, with the introduction rewritten here.
Top comments (0)