Buy One Get One 50% Off: Real Discount and Shopify Setup

Buy one get one 50% off means the cheaper of two items is half price, when both come from the same products or collection. On two items at the same price that is 25% off the pair; when prices differ it is less, because the discount lands on the lower-priced item. If the shopper would have bought one unit anyway, the promotion only earns more per order than that single full-price sale when your gross margin is 50% or higher. On Shopify you build it as a Buy X get Y discount: the customer buys 1 item and gets 1 item at a discounted value of Percentage 50.

Below: the arithmetic behind those two numbers, the native setup, the reasons it only discounts one item in a four-item cart, and a test checklist. The step-by-step fields that BOGO 50% shares with BOGO free are in our buy one get one free guide, so they are not repeated here.

What the shopper really saves

The effective discount on the pair is 0.5 × cheaper price ÷ pair total. Shopify's help page states the rule that decides which item that is: when the same product or collection is in both the "buys" and the "gets" section, "the lower-priced item that the customer chooses is the item that the customer gets at a discount" (Shopify Help Center).

So when both items come from the same products or collections, BOGO 50% is never more than 25% off the pair. If the buy and get sides are different products or collections, the rule changes: the item in the "gets" set is discounted, whatever its price.

The margin math

Take a unit price P and a gross margin m, so one unit costs (1 − m) × P. Profit per order is then m × P for one unit at full price, (2m − 0.5) × P for BOGO 50%, (m − 0.25) × P for 25% off one unit, (2m − 1) × P for BOGO free and (3m − 1) × P for buy 2 get 1 free. Here is that at P = $40:

Three things follow from the formulas:

• BOGO 50% beats a full-price single sale when 2m − 0.5 ≥ m, that is at m ≥ 50%. Buy 2 get 1 free has the same threshold (3m − 1 ≥ m).
• Below 50%, you need new pair orders on top of the shoppers who would have bought one anyway. If N of them now take the pair and X new pair orders arrive, the promotion breaks even when X ÷ N ≥ (0.5 − m) ÷ (2m − 0.5): 34 per 100 at a 40% margin, 200 per 100 at 30%. At 25% or below, no volume is enough.
• A pair sold to someone who would not have bought at all is profitable at any margin above 25%. BOGO free never beats a sale that would have happened anyway, because 2m − 1 is always less than m.

BOGO 50% vs 25% off vs BOGO free

For a shopper who buys two $40 items, BOGO 50% and 25% off everything cost the same: $60. The difference is the shopper who wants one. With 25% off they pay $30 and you keep $14 instead of $24 (at 60% margin). With BOGO 50% they pay full price, and the discount only goes to people who take a second unit. Against BOGO free, BOGO 50% gives away half as much per pair: $20 instead of $40 at P = $40.

Framing matters too. Chen, Marmorstein, Tsiros and Rao found that shoppers tend to prefer an extra-product offer over a price discount of the same economic value, because they neglect the base the percentage is taken from (Journal of Marketing, 2012). Pick BOGO 50% when your margin is around 50% or more and you want to move units in pairs; pick BOGO free only when the second unit costs you little; pick a flat percentage when single-unit orders are the norm.

Set it up in Shopify

1. In Shopify admin go to Discounts → Create discount → Buy X get Y, and choose an automatic discount or a discount code.
2. Customer buys: Minimum quantity of items, 1, from the products or collections in the deal.
3. Customer gets: quantity 1 from the same products or collections, At a discounted value → Percentage → 50.
4. Maximum number of uses per order: optional. Leave it off if every pair should get the discount; tick "Set a maximum number of uses per order" only if you want a cap.
5. Set Combinations and Active dates, then save.

Field-by-field notes (eligibility, limits, the code vs automatic choice) are the same as for BOGO free and are in the BOGO free guide.

5 things that break a BOGO 50%

1. Only one item discounted in a four-item cart. In a Shopify Community thread, a merchant running a buy one get one 40% off saw only one of four items discounted, without a maximum number of uses per order set. Shopify's help says that setting limits how many times the promotion applies per order (Shopify). So check the cap first, then run the 4-unit test cart below before launch and see what checkout actually does.
2. The second item is not added for the shopper. "The free or discounted 'get' item is never automatically added to the cart" (Shopify). Tell shoppers to add two on the product page.
3. Mixed prices. The cheaper item is the discounted one, so a $60 + $20 pair saves $10, not $30.
4. Stacking. On plans other than Plus, "all products that are part of a Buy X get Y discount are ineligible for further product discounts"; product discounts on other items can still combine (Shopify, combining discounts). For deliberate control over which deal wins, see stop discounts stacking.
5. The 25-discount cap. A store can have at most 25 active automatic discounts, and "this total includes app-based discounts" (Shopify).

The "50% off" price rule

In the US, the FTC's pricing guides cover this exact offer. The section on bargain offers tied to buying other merchandise names "Buy One—Get One Free", "Half Price Sale" and "50% Off", and says the price of the item the shopper must buy should not be raised for the promotion, and that the offer's terms should be stated clearly at the outset (16 CFR 233.4). In practice: do not raise the base price before the promotion starts, and show the conditions (which items, how many, any per-order cap) next to the offer.

If you also show a compare-at price, the guides say a former price should be one at which the item was openly and actively offered for sale, in good faith, for a reasonably substantial period (16 CFR 233.1). And remember the 50% is taken from the item's current selling price, not the compare-at.

When native is not enough

App discounts run as Shopify Functions that can target specific cart lines and quantities. BOGOify's BOGO offer uses that to:

• pick products and up to 20 collections on each side of the deal;
• take a percentage off, or a fixed amount per pair;
• discount every pair the cart earns, cheapest units first, as one Shopify discount, so a 4-unit cart gets two half-price units;
• run automatically or behind a code;
• show storefront messages while the offer is live, so shoppers know to add the second item.

Setup is in the BOGO guide. If a BOGO overlaps a volume discount, offer groups let one deal win per cart. For other apps, see our BOGO app comparison.

Test carts before launch

Offer under test: buy 1, get 1 at 50% from the same product or collection, uses per order not capped. Expected results:

• Test in a real checkout, not only the cart page.
• Try a cart with a discount code on top of the automatic deal.
• Check the order confirmation shows which line got the 50%.

FAQ

Is buy one get one 50% off the same as 25% off?

Only for two items at the same price, and only for shoppers who buy two. With mixed prices from the same set it is less than 25%, and a shopper who buys one gets nothing.

Which item gets the 50% off?

The lower-priced one, when both items come from the same products or collection. Otherwise the item in the "gets" set.

Can it repeat for every pair?

That is the intent when no maximum number of uses per order is set; the setting exists to limit how many times the deal applies in one order. Shopify's help does not spell out the 4-unit case, and merchants have reported only one discounted item, so put four units in a test checkout before launch.

Does it stack with a sitewide sale?

On plans other than Plus, items in a Buy X get Y take no further product discount. An order discount can combine if both discounts' combination settings allow it.