How Discounts Really Work (and the Double-Discount Trap)
Sales are full of percentages: 20% off, an extra 10% at checkout, buy-more-save-more. Working out the actual price in your head is tricky, especially when offers are stacked. This calculator does it for you and shows how much you really save. Use the free Discount Calculator above to try your own numbers instantly.
Single discount
Sale price = Original price × (1 − Discount ÷ 100). A 20% discount on 5,000 gives 5,000 × 0.80 = 4,000, a saving of 1,000.
Stacked discounts
When a shop offers "20% off plus an extra 10%", the second discount applies to the already reduced price, not the original. So the total is not 30%:
- 5,000 − 20% = 4,000
- 4,000 − 10% = 3,600
- Total saving = 1,400, which is 28%, not 30%.
The "Real combined discount" line in the calculator shows this true figure, so you can compare offers fairly.
Adding sales tax
In many places, tax is added at checkout on the discounted price. Enter the tax rate to see the price you'll actually pay at the till.
How to find the original price from a sale price
If you only know the discounted price, divide it by (1 − discount ÷ 100). For example, an item selling for 4,000 after 20% off had an original price of 4,000 ÷ 0.80 = 5,000.
Percent off vs amount off
Some offers give a fixed amount off instead of a percentage. To compare them, turn the amount into a percentage: 500 off a 2,500 item is 500 ÷ 2,500 × 100 = 20% off. On cheaper items a fixed amount is often the better deal, while on expensive items a percentage usually saves more.
Smart shopping tips
- Compare final prices, not discount percentages. A 50% discount on an inflated "original" price can be worse than 20% off elsewhere.
- Watch delivery and service fees, which can cancel out a discount online.
- Ask whether you need it. A purchase you didn't plan isn't a saving, however big the discount.
Planning further? You may also find our Income Tax Calculator, GST & Sales Tax Calculator useful, or explore all calculators.
Further reading: Discounts and allowances (Wikipedia)