If you set a free shipping threshold by copying another store, you are guessing with your margin.
That is the mistake.
Founders see another brand offering free shipping over $80 or $100 and assume they need a similar number. But a free shipping threshold is not just a promotional line in the header. It is part of your offer design. If you get it wrong, you can make carts look bigger while quietly making each order worse.
The right threshold does two jobs at the same time:
- It gives the customer a believable reason to add something useful to the cart.
- It leaves enough contribution margin to absorb the shipping cost you are taking on.
That is why the threshold should come from your own store economics, not from competitor mimicry or average order value alone.
The practical formula
Start with this:
Required basket uplift = average shipping subsidy ÷ incremental contribution margin rate
Then:
Starting threshold = realistic baseline basket + required basket uplift
That gives you a grounded starting point. Not the final answer. Just the first number worth testing.
Get the inputs right before you do the maths
The formula is only useful if the inputs are honest.
1. Use a realistic baseline basket
Average order value is a starting point, not the whole answer.
If a few large orders are pulling your average up, you can end up setting a threshold that looks sensible on paper and feels impossible in a normal cart. Look at:
- average order value
- median order value
- the order ranges most customers actually sit in
- how far typical carts are from the threshold you are considering
You are trying to answer a simple question: what basket are we actually trying to move?
2. Use contribution margin, not just gross margin
This is where a lot of free shipping advice gets lazy.
You do not pay shipping out of revenue. You pay it out of what is left after the order's variable costs are covered.
That means the useful number is contribution margin after costs such as:
- cost of goods
- payment fees
- pick and pack
- packaging
- variable fulfilment costs
- order-level discounts
If you ignore those, the threshold can look profitable when it is not.
3. Use the shipping cost you actually absorb
Do not use the best-case carrier rate because it makes the spreadsheet feel nicer.
Use the shipping subsidy the business is really taking on for the orders that will qualify. If costs swing hard by parcel size, region, or product type, you need to know that before you set one clean sitewide number and hope for the best.
A quick worked example
Say your typical basket is $80.
Your average shipping subsidy on qualifying orders is $10.
The incremental contribution margin rate on the products people are likely to add is 55%.
The uplift needed to cover shipping is:
$10 ÷ 0.55 = $18.18
So the starting threshold is:
$80 + $18.18 = $98.18
That probably means a customer-facing threshold of $99 or $100.
That is the right kind of answer because it is grounded in the economics first. Now you can ask the second question: can customers realistically reach it?
The formula is only half the job
The store's number can be correct and the offer can still underperform.
Why? Because customers do not respond to formulas. They respond to what is in front of them in the cart.
Check whether the gap is reachable
If most carts would need to add one sensible item, the threshold may work.
If most carts would need two or three unrelated products, it probably will not.
That is where product discoverability matters. The threshold needs a believable path.
Ask:
- what is the common gap between the cart and the new threshold?
- what products would customers naturally add to close it?
- do those products actually improve the purchase?
- do those products still leave enough contribution after shipping?
If the gap can only be closed with random low-margin add-ons, you do not have a strong threshold. You have a forced upsell.
Avoid the wrong product mix
This part gets missed all the time.
The additional spend only helps when the added product is commercially useful. If the threshold gets closed with sale items, bulky products, or low-margin products, the business can be worse off even though AOV rises.
That is why free shipping should sit inside the wider offer design conversation. It is not there to increase the cart at any cost. It is there to make a better order that still works for the store.
The common mistakes
Most weak free shipping thresholds fail in one of four ways.
The threshold is too low
If most orders would have qualified anyway, you are not changing behaviour. You are just giving shipping away.
The threshold is too high
If customers need to rebuild the order to hit it, the offer stops feeling achievable and gets ignored.
The maths ignores discount stacking
Free shipping plus a percentage discount plus a bundle deal can look generous to the customer and ugly to the margin. The rule needs to make sense after the full promotion stack, not before it.
The store shows the offer without helping the customer act on it
If the header says "Free shipping over $100" but the cart does not help people find a sensible extra item, the message is just decoration.
Test profit, not just AOV
This is the part that matters most.
A higher average order value is not enough on its own. A threshold is only doing its job if the extra basket value creates better commercial outcomes after the shipping subsidy is covered.
Track the change against:
- conversion rate
- average order value
- median order value
- contribution per order
- shipping cost per qualifying order
- free-shipping uptake
If you want a clean before-and-after baseline on the conversion side, run the Conversion Rate Calculator before you make the change. Then compare the live result with the margin outcome, not just the top-line order value.
When one threshold is the wrong answer
Some stores should not force one universal number.
That can happen when:
- shipping costs vary a lot by region
- bulky products distort fulfilment costs
- low-margin categories should not qualify
- subscription orders need a different policy
In those cases, the fix may be a narrower rule, a regional condition, a discounted shipping offer, or a stronger bundle rather than one broad free-shipping promise.
The point is not to force free shipping to work because it is common. The point is to use it when it strengthens the offer without quietly hurting the business.
The better way to use this formula
Use the formula to get to a defensible starting point.
Then pressure-test it against real carts, real add-on products, real shipping costs, and real margin.
If the threshold sits above current basket behaviour but still feels reachable, and the added spend actually covers the subsidy, you are in the right zone.
If not, change the rule. Do not keep a weak threshold just because "free shipping" sounds like good ecommerce hygiene.
Start with diagnosis if you are still guessing
If you are not sure whether free shipping is actually the right lever, run the Store X-ray first. It is the better cold step when the real problem might still be traffic quality, page alignment, offer design, or friction somewhere else in the journey.
If you already suspect the issue is wider than cart incentives and want the likely layer confirmed, take the Revenue Bottleneck Quiz.