Sale Price Calculator
Calculate a discounted price, the total saving and the effective additional discount from stacking offers.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
Stacked discounts multiply rather than add: 20 percent off then another 20 percent off is a 36 percent total reduction, not 40. Knowing the true effective discount stops a two-part offer from looking better than it is.
Worked example
calculated with the default values below
Original price 120 $ · First discount 20 % · Second discount (stacked) 10 % · Sales tax 0 % · Shipping 0 $ · Coupon value 0 $ Price after the first discount 96.00 $ · Price after all discounts 86.40 $ · Effective total discount 28.00 % · Total saving 33.60 $ · Final total including tax and shipping 86.40 $
General background references
Disclaimer
These calculators give general estimates. Sizing, pricing, availability and standards vary by brand, retailer and country, so treat the output as a starting point and confirm it against the seller's or authority's own figures.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
S = P(1 - d1 ÷ 100)(1 - d2 ÷ 100) - c; total = max(0,S) × (1 + t ÷ 100) + ship
- P
- Original price
- d1/d2
- First and stacked discount (%)
- c
- Coupon amount
- t
- Sales tax (%)
- ship
- Shipping
Discounts are applied sequentially, then the coupon is subtracted (not below zero); tax is applied to the discounted amount and shipping is added afterward. Effective discount is undefined when the original price is zero. Local tax treatment of shipping may differ.
Frequently asked questions
Why do stacked 20 and 10 percent discounts make 28 percent off?
Discounts multiply rather than add, so 20 percent off leaves 80 percent of price, and the second 10 percent cuts that remainder, not the original, giving a 28 percent total reduction instead of 30. On 120 dollars the first drop takes it to 96, and the second to 86.40, a 33.60 saving. The effective discount line reports the true combined figure so a two-part offer cannot look better than it is.