How to work out a discount
A discount calculator answers the question every shopper actually has at the shelf: what will this cost after the sale, and how much am I really saving? Enter the original price and the percentage off, and you get the final price, the money saved, and the saving as a share of what you would have paid. It works equally well for retail sales, supplier quotes and invoice discounts.
How to use the Discount Calculator
- Enter the Original Price before any reduction.
- Enter the Discount (%) — 25 for a quarter off.
- Read the final price and the amount saved together.
- Change the percentage to compare two offers on the same item.
Formula and a worked example
Saving = Price × (d ÷ 100) · Final = Price − Saving
An equivalent shortcut is Final = Price × (1 − d ÷ 100), which is quicker for mental maths: 30% off means paying 70% of the price. Stacked discounts multiply rather than add — 20% off then a further 10% off is 0.8 × 0.9 = 0.72, so 28% off, not 30%.
Worked example
A jacket listed at 4,500 with 35% off: the saving is 4,500 × 0.35 = 1,575 and you pay 2,925. If a second shop offers 20% off then another 20% at the till, you pay 0.8 × 0.8 = 64% of the price — a 36% discount, slightly better than the single 35%.
Frequently asked questions
How do I calculate a percentage off in my head?
Take 10% by moving the decimal one place, then scale. For 35% off 4,500: 10% is 450, so 30% is 1,350, half of 450 is 225 for the extra 5%, total 1,575.
Do two discounts of 20% add up to 40%?
No. They multiply: 0.8 × 0.8 = 0.64, which is a 36% discount overall.
How do I find the original price from a sale price?
Divide the sale price by (1 − discount). An item at 2,925 after 35% off was 2,925 ÷ 0.65 = 4,500.
Is the discount applied before or after tax?
Almost always before. Work out the discounted price first, then apply sales tax or GST to that figure.
Related calculators
Other tools people use alongside the discount calculator.