Stacked Discount Calculator

How it is calculated

The two percentages are applied one after the other, not added. final = price × (1 − d1/100) × (1 − d2/100), saved = price − final and effective % = saved ÷ price × 100. The second discount works on the price left after the first, so the effective rate is always lower than d1 + d2 as long as both are above zero. Because multiplication is commutative, the order of the two discounts does not change the final price.

The price must be zero or more, and each discount must be between 0 and 100; a discount of 120, or a negative price, gives no result. A 100% discount makes the final price zero. Amounts are shown in dollars with two decimals. Tax, shipping and minimum-spend conditions are not included.

Common mistakes

• Adding the percentages (30% + 15% = 45%). The second discount applies to the already-reduced price, so the real saving here is 40.50%.
• Applying the second percentage to the original price instead of the sale price, which overstates the saving.
• Assuming the order matters. 15% then 30% gives exactly the same $47.60 as 30% then 15%, so only the two percentages count.
• Typing a discount as a decimal (0.30) instead of a percent (30), which gives almost no discount.
• Expecting the result to include VAT or sales tax. It is calculated on the shelf price only, so add tax after the discounts if it applies.