Which order to apply a percentage and a flat coupon. Percentage first is always at least as good, because applying the flat amount first shrinks the base the percentage works on.
Also called: stack coupons, coupon order.
$81.00 by applying the percentage coupon first. Percentage first gives $81.00 and flat first gives $84.00, a difference of $3.00.
A flat coupon applied before a percentage reduces the amount the percentage can discount, so you lose the percentage of the flat coupon. Percentage first preserves the full base, then the flat amount comes off in full. The difference is exactly the percentage times the flat coupon, which on a large flat voucher is not trivial. Checkouts vary in which order they apply, and some let you choose.
applying a flat amount before a percentage discounts the flat amount tooEach of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.
Best achievable price$81.00
Percentage first: 120 x 0.8 = 96, less 15, is 81. Flat first: 105 x 0.8 = 84. The 3 difference is exactly 20% of the 15 voucher, which is the general result and the reason order matters.
Open this exampleBest achievable price$96.00
boundary: with nothing for the percentage to be applied before or after, both orders give 120 x 0.8 = 96
Open this exampleBest achievable price$120.00
degenerate case: nothing applied leaves the cart exactly as it was
Open this exampleFormula version 1.0.0 · definition 1.0.0 · United States · Report a problem with this calculator