How to Calculate a Discount (Percent Off & Sale Price)

By the Tool Goodie Team · Updated July 4, 2026 · 4 min read

To calculate a discount, multiply the original price by the percent off divided by 100 to find the amount saved, then subtract it from the price. So 25% off an $80 item saves $20, for a $60 sale price. Below is a faster mental method, plus the one thing that catches everyone out — how "stacked" discounts really combine.

Key takeaways

Saved = price × (percent ÷ 100). Sale price = price − saved.
Mental method: find 10% (move the decimal left), then scale.
Stacked discounts multiply — "20% then 10%" is 28% off, not 30%.
Check any deal with the discount calculator.

The formula

Amount saved = price × (percent ÷ 100)
Sale price = price − amount saved

Examples:

25% off $80 → 80 × 0.25 = $20 saved → $60 sale price
30% off $50 → 50 × 0.30 = $15 saved → $35 sale price

A shortcut: the sale price is just the price times (1 − percent). 25% off means you pay 75%, so $80 × 0.75 = $60 in one step.

The fast mental method

Use the 10% trick: 10% of any price is that price with the decimal moved one place left, then scale to the discount you need.

30% off $50 → 10% is $5 → ×3 = $15 off → pay $35
15% off $40 → 10% is $4, plus half ($2) = $6 off → pay $34

Is the deal as good as it looks? The free Discount Calculator shows the sale price, the amount saved, and — with a second discount or sales tax — the final amount you actually pay.

Why stacked discounts don't simply add

Here's the trap. When a store offers "20% off, then an extra 10% at checkout," that is not 30% off. The second discount is taken from the already-reduced price, so:

Start at 100% of the price.
After 20% off, you're at 80%.
After a further 10% off that, you're at 90% of 80% = 72% of the original.

So the true combined discount is 28%, not 30%. The same logic applies to a discount plus a coupon, or a sale price plus a member discount — they always multiply, never add. It's worth checking, because "30% off" and "20% + 10%" are advertised as if they're the same, and they're not.

Frequently asked questions

How do you calculate a discount?

Multiply the original price by the discount percentage divided by 100 to get the amount saved, then subtract that from the price. For example, 25% off $80 saves $20, giving a sale price of $60.

How do stacked discounts work?

A second discount applies to the already-reduced price, not the original. 20% off then an extra 10% off is not 30% off; the item ends at 72% of the original price, a 28% total discount.

How do you quickly work out a percent off in your head?

Find 10% by moving the decimal one place left, then scale it. For 30% off $50: 10% is $5, so 30% is $15 off, giving $35.