Calculate sale prices, savings, and stacked discounts
Whether you are shopping during a sale, comparing deals across retailers, or working out the true cost of a "buy one get one half price" promotion, knowing how to calculate discounts quickly is a practical everyday skill. This discount calculator instantly shows you the sale price, savings amount, and effective discount percentage -- including support for stacked discounts where multiple promotions apply. Stacked discounts are common during major sales events like Black Friday, where a store might offer 20% off everything plus an additional 10% for loyalty card holders. A common misconception is that these add up to 30% off, but in reality the second discount applies to the already-reduced price, resulting in a total saving of 28%. This calculator handles the compound arithmetic correctly so you always know the true final price.
To calculate a discount: 1. Enter the original price of the item before any discounts are applied. 2. Adjust the discount slider to set the percentage discount. The slider ranges from 0% to 100%. 3. If there is an additional discount on top of the first (for example, a loyalty card discount or a further reduction in a clearance sale), toggle "Additional Discount?" to Yes and enter the second discount percentage. 4. View the results. The calculator shows the discount amount (how much the first discount saves), the final price after all discounts, total savings, and the overall effective discount percentage. 5. The pie chart visualises the split between the final price you pay and the total amount saved, making it easy to see the proportion at a glance.
The discount calculation uses simple percentage arithmetic, with an important distinction for stacked discounts. For a single discount: discount amount = original price x (discount percentage / 100). The final price is the original price minus the discount amount. For stacked (compound) discounts, the second discount is applied to the price after the first discount, not the original price. The formula is: price after first = original price x (1 - first discount / 100), then final price = price after first x (1 - second discount / 100). The total effective discount percentage is calculated as: (total savings / original price) x 100. This reveals the true combined discount rate. For example, GBP 100 with 20% off gives GBP 80. An additional 10% off GBP 80 gives GBP 72. Total savings = GBP 28, effective discount = 28%. The formula for the combined rate is: 1 - (1 - 0.20) x (1 - 0.10) = 1 - 0.72 = 0.28, or 28%.