How to Calculate the Real Price of Buy 1 Get 1 and Buy 2 Get 1
A "buy 1 get 1 free" tag feels like half price, and it is, but only when you take items in pairs. The real price depends on how many units you actually pay for.
The formula
For a "buy N get M free" deal, one group is N + M items and you pay for N of them.
- Units paid = (full groups × N) + the leftover items, up to N.
- Price per item = shelf price × units paid ÷ items taken.
Examples
- BOGO, 10 cans at $1.80: 5 groups of 2, you pay for 5. Total $9.00, $0.90 each.
- BOGO, 3 cans: one group of 2 plus 1 leftover, you pay for 2. Total $3.60, $1.20 each, not $0.90.
- Buy 2 get 1, 5 items at $3: one group of 3 (pay 2) plus 2 leftover (pay 2). You pay for 4: $12.00.
BOGO vs a percentage discount
BOGO equals 50% off per item only in pairs. Buy 2 get 1 equals about 33% off, only in groups of three. If you will not use the extra item before it spoils, a smaller plain discount on one item can be the better deal.
Doing it in the cart
In Aislemath, add the item, set the quantity with +, and pick 1+1 or 2+1. The row shows the original price crossed out and what you actually pay, and the cart total and savings update right away.