The True Cost of Free Shipping (And How to Offer It Profitably)
Set a free-shipping cart minimum where your contribution margin covers the shipping you absorb. If your average shipping cost is $9 and your contribution margin is 35%, you need about a $26 order for the margin to cover shipping. Below that threshold, free shipping costs you money on every order.
The free shipping tradeoff
Free shipping is one of the strongest conversion levers in ecommerce, but the postage does not disappear. Someone pays it, and if you have not planned for it, that someone is you. The goal is to capture the conversion lift without handing back your margin.
Setting a threshold that pays for itself
The cleanest approach is a free-shipping threshold: a cart minimum a customer must reach to unlock it. Set it where the contribution margin on that order covers the shipping you absorb. The formula is simple: threshold equals your average shipping cost divided by your contribution margin rate.
Threshold = shipping cost / contribution margin rate. At $9 shipping and a 35% margin, that is $9 / 0.35, or about a $26 cart minimum before free shipping breaks even.
A well-set threshold also raises average order value, because customers add items to qualify. That lift is often worth more than the shipping you give up above the threshold.
When to bake shipping into the price
For low-price single-item products where a threshold is impractical, the alternative is to raise the item price enough to absorb shipping. Customers strongly prefer a $28 item with free shipping over a $22 item plus $6 shipping, even though the total is identical. Just make sure the higher price still hits your net margin target.
Common pitfalls
- Setting the threshold below break-even, so you lose money on every qualifying order.
- Forgetting that returns on free-shipping orders cost you the outbound postage twice.
- Applying one threshold across products with very different shipping costs.
Frequently asked questions
Does free shipping actually increase sales?
Yes, it consistently lifts conversion and average order value, but only profitably if the threshold or price is set to cover the shipping cost you absorb.
What contribution margin should I use in the threshold formula?
Use the margin left after product cost, fees, and processing but before the shipping you are trying to cover, so the threshold reflects the money actually available to absorb postage.
Is a flat-rate shipping fee better than free shipping?
Flat rate protects margin and is simpler, but generally converts worse than free shipping. A threshold is often the best of both.
Related tools & guides
MerchSites tools and guides are written and reviewed by ecommerce practitioners. Calculations are cent-accurate estimations based on reported platform fees and standard formula math.