FAQ · the math behind the offer

BOGO deals: what "buy one get one" is actually worth

BOGO sounds like free money, and it's rarely priced like it. Half off the second item is a 25% discount on the pair; a true BOGO free deal is 50% — and only if you actually wanted two of the thing. Here's the conversion table for every BOGO variant, the uneven-price catch, and what a coupon on top really adds.

The equivalent-discount table

For two items at the same price, the conversion is mechanical: the second-item discount applies to only half the purchase, so the whole-purchase discount is half the headline:

The pattern: whole-purchase equivalent = second-item discount ÷ 2. So the "50% off everything" feeling of a BOGO 50% sign is, arithmetic honestly, quarter-off.

The catch: do you need both?

The table assumes the benchmark is buying two items anyway. If you need one, a BOGO offers you nothing — you either buy two to unlock the discount (total spend goes up) or skip it. The honest framings:

• You need two. Compare the BOGO pair price against two single purchases anywhere else — that's a real 50%/25%/30% comparison against a real baseline.
• You need one but will use two eventually. The discount is real only against the certainty you'll use the second before it expires — consumables and staples qualify; gadgets usually don't.
• You need one, full stop. The BOGO is decoration. Judge the first item's price on its own against the item's normal price — the anchor-price check applies exactly the same here.

Uneven prices

When the two items differ in price, most BOGO terms apply the second-item discount to the lower-priced item — which makes the whole-purchase discount even smaller than the ÷2 table. Example: $60 + $20 with second-at-50%-off pays $60 + $10 = $70 against a $80 list — 12.5% off the pair, not 25%. Some promotions cap the discounted item's price instead; the coupon or shelf face governs, so read which item absorbs the discount before assuming the headline math.

Stacking a coupon on top

Where the retailer allows a coupon on a BOGO purchase, the coupon percentage applies after the BOGO math — and like all stacked percentages, it multiplies rather than adds: a 20% coupon on top of a true BOGO free (50% equivalent) is 1 − (0.5 × 0.8) = 60% off the pair, not 70%. The calculator runs any variant plus coupon layers:

The multiplication rule behind the coupon layer is the same one that governs every stacked discount — the worked examples are in how to stack coupons, and the per-retailer rules on whether coupons ride along with promotional pricing at all are in the per-retailer coupon limits table.

BOGO terms — which item absorbs the discount, coupon eligibility, category exclusions — vary by retailer and promotion. The math above is the general conversion; the offer face and the retailer's coupon policy govern the specific deal.