What is this calculator?
This calculator finds the price after one or two discounts and the total saving. When two discounts apply, the second is applied to the already-reduced price, which is why two discounts never simply add together.
Use it when:
- You want the final price after a headline discount.
- A promotion stacks a second discount on an already-reduced price.
- You want to know the real combined percentage of two stacked offers.
Intended for: Shoppers checking an advertised offer, and sellers pricing a promotion.
How is this calculated?
- The first discount percentage is applied to the original price, producing an intermediate price.
- If a second discount is entered, it is applied to that intermediate price — not to the original — because that is how stacked offers actually work at the till.
- The amount saved is the original price minus the final price.
- The effective saving percentage is that saving expressed against the original price, which is always less than the two percentages added together.
Formulas
Final price
Final = Original × (1 − d₁/100) × (1 − d₂/100)
The discounts multiply rather than add, because the second acts on what is left after the first.
- d₁
- First discount percentage
- d₂
- Additional discount percentage (0 if none)
Effective saving
Effective % = (Original − Final) / Original × 100
The single discount that would have produced the same final price.
Example
An item priced 2,000 with 20% off, plus a further 10% off at checkout.
- After 20% off: 2,000 × 0.80 = 1,600.
- After a further 10% off that: 1,600 × 0.90 = 1,440.
- Total saving: 2,000 − 1,440 = 560.
Result: Final price 1,440, you save 560 — an effective discount of 28%, not 30%.
Frequently asked questions
Why is 20% plus 10% not 30% off?
The 10% is taken from the already-discounted price, not the original. 20% then 10% gives an effective 28%. Stacked discounts are always worth slightly less than their sum.
Does the order of the two discounts matter?
No. Multiplication is commutative, so 20% then 10% gives exactly the same final price as 10% then 20%.
Is tax included in the final price?
No. Enter pre-tax or post-tax prices consistently. If tax is applied after the discount, calculate the discount first and then apply tax to the result.
Assumptions
What this calculator takes as given:
- Both discounts are percentage discounts applied sequentially to the price.
- The price you enter is the basis for the first discount, before any tax or shipping.
Limitations
What this calculator cannot know or does not model:
- Flat-value discounts, minimum-spend thresholds, and capped discounts are not modelled.
- Tax, shipping, and payment-method offers are not included.
- Rounding applied by a retailer's own till system may shift the final figure slightly.