Buy one get one free calculator
See what a buy-one-get-one offer is really worth per item, and compare it against a plain percentage discount on the same product.
Your numbers
The normal price before the offer.
How many you pay for.
How many you get free.
Enter a percentage offer on the same product.
Result
Enter your numbers and the result appears here.
How this is calculated
- You pay for one item and take home two, so the real discount is free items divided by total items.
- Buy one get one free is 1 / 2 = 50%; buy two get one free is 1 / 3 = about 33.3%.
- The effective price per item is what you pay divided by the number of items you receive.
- Enter a comparison discount and the calculator shows which offer gives the lower price per item.
- Everything is calculated in your browser.
Formula
- Real discount
discount = free items / (paid items + free items) x 100- Effective price per item
price per item = (price x paid items) / (paid items + free items)- Straight discount comparison
discounted price = price x (1 - discount / 100)
Worked example
Milk at 4.00 is on buy one get one free. The same milk is 40% off in another aisle.
- BOGOF: 4.00 for two, so 2.00 each — a real 50% discount
- 40% off: 4.00 x 0.6 = 2.40 each
- Gap: 2.00 against 2.40, so BOGOF is about 16.7% cheaper
The BOGOF offer wins by 0.40 per item — but only if you will use both before they spoil.
Things to watch for
- Two items you cannot use is not a saving. Watch expiry dates on fresh items in particular.
- Prices are sometimes raised before a multibuy promotion. Check the usual price where you can.
- The free item is occasionally a smaller size. If the sizes differ, compare per 100 g or per 100 ml instead.
- If you only need one, a multibuy increases what you spend even though the unit price falls.
Frequently asked questions
Why is buy one get one free a 50% discount?
You pay for one item and receive two, so the price per item is halved. The unit price behaves like a 50% discount, but your total spend does not fall — you are buying twice the quantity.
Is BOGOF the same as 50% off?
The price per item is the same, but the situation is not. At 50% off you can buy a single item at half price; with BOGOF you must take two. For anything you use slowly, the straight discount is better.
Can I model buy two get one free?
Yes — change the paid and free quantities. Buy two get one free is about 33.3%; buy three get one free is 25%.
What if the free item is a different size?
This calculator assumes identical items. When sizes differ, work in total weight or volume using the price per 100 g or per 100 ml calculator.
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Last reviewed: August 25, 2026
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