When does bundling improve contribution?
A bundle changes two things at once: the revenue collected for the items and the cost of fulfilling their order. Shipping and fixed processing fees may fall, while a price discount or extra packaging may absorb those savings. This calculator compares exactly one unit of item A and one unit of item B in both scenarios.
Use it before replacing two separate listings with a combined offer. Enter the shipping amount you pay for each separate order, then the total shipping for the combined package. If item A and item B have different separate shipping costs, enter their average in the separate-shipping field; the model multiplies that amount by two. Include ordinary packaging in the shipping/fulfillment figures and put only the additional bundle packaging in its own field.
The formula, term by term
Let r be the combined percentage charge divided by 100, C the two acquisition costs added together, F the fixed fee per order, S the shipping per separate order, B the bundle price, T the bundle shipping and K the extra packaging.
Bundle contribution = B × (1 − r) − C − F − T − K
Bundle margin (%) = bundle contribution ÷ B × 100
Zero-contribution bundle price = (C + F + T + K) ÷ (1 − r)
The last expression requires combined percentage charges below 100%. At 100%, increasing revenue cannot cover positive entered costs. A zero selling price also has no defined percentage margin.
Worked example: the discount outweighs shipping savings
Item A sells for $25 and costs $10; item B sells for $20 and costs $7. The bundle sells for $39. Percentage fees are 10%, shipping is $5 for each separate order or $6 for the bundle, and extra bundle packaging costs $1. There is no fixed fee.
| Scenario | Calculation | Contribution |
|---|---|---|
| Separate orders | $45 − $17 − $4.50 − $10 | $13.50 |
| One bundle | $39 − $17 − $3.90 − $6 − $1 | $11.10 |
The bundle contributes $2.40 less, with a 28.46% margin before unentered costs. Its zero-contribution price is $24 ÷ 0.90 = $26.666… (displayed as $26.67). That threshold does not match the separate-order profit. To preserve the $13.50 separate contribution, the bundle needs $37.50 ÷ 0.90 = $41.666… before rounding. If setting a real price to meet a threshold, round upward to the next cent.
Interpret the result before changing a listing
A positive comparison means the bundle retains more of the entered revenue for the same items. It does not show whether buyers prefer a bundle, whether inventory sells faster, or whether advertising costs change. Add the cost of inserts, fragile packaging or fulfillment surcharges to the relevant entered costs. Monthly overhead, acquisition advertising and refunds remain outside this model unless allocated into those costs.
The percentage fee is applied to item revenue only. If your platform charges fees on customer sales tax or separately charged shipping, calculate an effective rate for your scenario or use a more detailed fee model. Do not treat the example rate as a current marketplace quote.