How to Calculate Discounts on Your Purchases and Save Money
Published on 3 de marzo de 2026 | Recently updated
Learn to calculate simple and successive discounts, avoid commercial traps and discover strategies to buy intelligently.
Understanding discounts: beyond the percentage on the label
Sales, promotions and offers are everywhere: Black Friday, summer sales, online coupons, volume discounts. Knowing how to calculate exactly how much you save (and how much you actually pay) is a basic financial skill that can cost you hundreds or thousands of euros a year. It's not just about applying a percentage; It is about comparing, evaluating and deciding judiciously if an offer is worth it.
The good news is that the calculation itself is simple. The Discount Calculator GlobalTool gives you the result instantly, but understanding the logic behind it makes you a much smarter consumer.
The basic discount formula
Calculating a discount involves two simple operations:
Discounted amount = Original price × (discount percentage / 100)
Final price = Original price − Discounted quantity
Example: an item costs €89.99 with a 30% discount.
- Discount = 89.99 × 0.30 = €27.00
- Final price = 89.99 − 27.00 = €62.99
You can also calculate directly by multiplying by the complementary: 89.99 × 0.70 = €62.99. If you want to practice these types of shortcuts, check out our article on tricks to calculate percentages mentally.
Successive discounts: the mistake most people make
One of the most frequent mistakes is adding successive discounts as if they were one. If a store offers a 20% discount and then applies an additional 10%, the total discount not is 30%.
Beware of chained discounts
An additional 20% + 10% equals a total 28%, not 30%. It is calculated like this: (1 − 0.20) × (1 − 0.10) = 0.72. That is, you pay 72% of the original price.
To avoid mistakes, use the Percentage Calculator and apply discounts sequentially. Or directly enter the data in the Discount Calculator to get the exact final price.
Table: how much you really save according to the discount
| Original price | 10% | 20% | 30% | 50% |
|---|---|---|---|---|
| €25 | €22.50 | €20.00 | €17.50 | €12.50 |
| €50 | €45.00 | €40.00 | €35.00 | €25.00 |
| €100 | €90.00 | €80.00 | €70.00 | €50.00 |
| €200 | €180.00 | €160.00 | €140.00 | €100.00 |
| €500 | €450.00 | €400.00 | €350.00 | €250.00 |
Strategies to be a smart buyer
Not every discount is a good deal. Here are some strategies to distinguish real bargains from commercial traps:
- Compare the price per unit. Sometimes the “large discount” container is still more expensive per gram than the small container at full price. The Rule of Three helps you calculate the unit cost quickly.
- Research the historical price. Some stores raise the price before sales to make the discount appear larger than it is.
- Calculate the real cost of the "3×2". A 3×2 is equivalent to a 33.3% discount, not the 50% that seems intuitively.
- Don't buy just because there is a discount. A 40% savings on something you don't need is still a 60% expense.
- Take advantage of cashback and cumulative coupons. But don't waste more time searching for coupons than the savings you get are worth.
If you want to keep greater control of your home economy, read our guide on how to plan your personal finances. And if you buy in international stores with prices in other currencies, the Currency Converter will allow you to compare prices in your local currency instantly.
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