How a discount is calculated
The sale price is the full price multiplied by (100 − discount) ÷ 100. An $80 item at 30% off costs 80 × 0.70 = $56, and you save $24. Alternatively, work out the discount first (80 × 30 ÷ 100 = 24) and subtract it.
Double discounts don't add up
Sales often advertise "30% off plus an extra 20% at checkout". The total is not 50%: the second discount applies to the already reduced price. From $80 you go to $56, then to 56 × 0.80 = $44.80, an effective discount of 44%. The calculator shows exactly that effective total discount, so you are not misled.
Finding the discount from two prices
If you know the full price and the final price, the discount is (full − final) ÷ full × 100. From $120 to $89.90 the discount is 25.08%. Handy for comparing offers or checking that a price tag tells the truth.
Shopping tips
- Always compare the final price, not the percentage: 40% off an inflated price can cost more than 20% off an honest one.
- In online shops, check whether the discount applies before or after shipping costs.
- For mental maths: 25% is a quarter, 50% is half, 10% is the number with the decimal point moved one place.
Frequently asked questions
How do I take 30% off a price?
Multiply the price by 0.70 (that is 100% − 30%). On $80 you get $56.
Do two 20% discounts equal 40%?
No: the second applies to the already discounted price, so two 20% discounts equal 36% (0.8 × 0.8 = 0.64).
Does the calculator handle cents?
Yes, results are shown with two decimals; you can enter decimals with a point or a comma.