Buy X Get Y Calculator
BOGO and Buy 2 Get 1 Free are both special cases of a more general "buy X, get Y free" mechanic. Enter any X and Y to evaluate the exact profit impact.
Contribution profit per order
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Customer pays
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Total units delivered
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Margin
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Effective discount
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vs. one regular-price sale
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Volume uplift needed
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Setting X=1, Y=1 reproduces classic BOGO. Setting X=2, Y=1 reproduces Buy 2 Get 1 Free. Any other combination (buy 3 get 2, buy 5 get 1) is evaluated with the same underlying formula.
How it works
Formulas used
Revenue = X × Unit price Units delivered = X + Y Product cost = (X + Y) × Unit cost Effective discount = 1 − [Revenue / (Regular price × Units delivered)]
Worked example
$30 unit price, $8 unit cost, buy 3 get 2 free, no fees:
- Revenue: 3 × $30 = $90 for 5 units
- Product cost: 5 × $8 = $40
- Contribution profit: $90 − $40 = $50 (margin 55.6%)
- Effective discount: 1 − (90/150) = 40%
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Frequently asked questions
How do I decide the right X and Y for my business?
Higher Y (more free units) drives a bigger perceived deal but a bigger profit hit — use the required volume uplift figure to judge whether it is likely to pay off versus your historical promotion response.
Test the exact X-for-Y structure
Small changes to the paid and free quantities can materially change effective discount and inventory use. Model the actual mechanic rather than assuming every multi-buy behaves like standard BOGO.
Compare structures
- Calculate several X and Y combinations using the same product and fee assumptions.
- Choose a threshold that is meaningfully above the customer’s normal quantity.
- Check whether a fixed bundle price is easier to explain than a free-unit rule.
Rule design
- Define whether the lowest-priced eligible item becomes the free item.
- Limit redemptions when inventory or reseller abuse is a concern.
- Make returns policy consistent with the allocation of discount across all units.