Two break-evens, and they answer different questions
Ask where free shipping breaks even and there are two defensible answers depending on what you think free shipping is doing.
The first treats the whole order as being at stake. The customer came because of the offer, so the entire order has to pay for itself: contribution on the order value must cover pick, pack and the shipping you absorb. That gives the higher threshold, and it is the right one when free shipping is what wins the order.
The second treats only the shipping charge as being at stake. The customer was buying anyway and would have paid the shipping charge. Giving it away costs you exactly that charge, and the margin on whatever they add to reach the threshold has to replace it. That gives a lower threshold, and it is the right one when free shipping is a promotion layered onto established demand.
Most businesses are somewhere between the two, which is why both are shown rather than one. If you cannot tell which describes you, use the higher one, because being wrong in that direction costs you volume and being wrong in the other direction costs you money on every order.
Contribution per dollar is the whole calculation
Everything reduces to one rate: what a marginal dollar of order value is actually worth to you. Gross margin less the fees charged on the order value, because those scale with the order and a fixed cost does not. At 42 percent margin and 3.4 percent in fees, a dollar of order value is worth 38.6 cents of contribution.
Divide the cost you are absorbing by that rate and you have the threshold. If shipping and pick and pack come to $11.60, then $11.60 divided by 0.386 is $30.05, and that is the order value at which the contribution exactly covers what you spent. Below it you are subsidising the order. Above it the excess is your profit on it.
The single most common mistake is dividing by the gross margin rather than by the contribution rate, which ignores the fees and produces a threshold that is a few percent too low across every order. The second most common is dividing by nothing at all and setting the threshold equal to the shipping cost times some multiple that felt right.
The number nobody has
| Input | Where it comes from | How wrong it usually is |
|---|---|---|
| Gross margin | Your accounts | Reliable, if it is by order rather than by product |
| Fees | Your statements | Reliable, though often understated by forgetting fixed per-transaction charges |
| Pick, pack, materials | A time study and a materials count | Usually understated, because labour gets left out |
| Shipping cost | Your carrier invoices, blended | Understated, because surcharges arrive on a later invoice |
| Share who top up | Nowhere. It is a guess. | Completely unknown until you measure it |
The last row is the one that makes the monthly projections soft. There is no published figure for how many customers will add items to reach a threshold, because it depends entirely on your catalogue, your prices and the gap they have to close. What is knowable is your own answer, measured by running a threshold and watching what happens to the distribution of order values, not just the average. A threshold that works shows up as a spike in orders just above it.
What to do with the answer
Set the threshold at or above the break-even, not below it. A threshold set below break-even loses money on every order that lands between the threshold and the break-even point, and those are precisely the orders the threshold attracts, so the loss is concentrated rather than incidental.
Then watch the gap. If your break-even sits well above your average order, the threshold is asking customers for a jump they will not make, and the lever is the shipping cost or the packaging rather than the threshold. That is a good moment to go back to the void fill calculator and see whether the box is setting the freight bill, and to the freight quote comparison if the shipments are large enough to move as freight. If you are the customer on the other side of one of these thresholds rather than the seller, the buyer-side version works out whether adding items beats paying the shipping.
Questions people ask
Why is my break-even higher than my competitor's threshold?
Because thresholds are copied and break-evens are calculated. A competitor with a higher margin, a lighter product, a cheaper shipping rate or more units per order has a genuinely lower break-even, and a competitor with none of those may simply be losing money on the offer and funding it from somewhere else. Neither is a reason to match the number. What you can usefully copy is the structure of their offer, not the figure in it, and the figure has to come out of your own contribution rate.
Should I just raise prices and offer free shipping on everything?
That is a real option and it changes the question rather than answering it. Building shipping into prices means every order pays for it, including the small local ones that were cheap to ship, and it makes your headline prices higher against competitors who charge shipping separately. It works well where orders are uniform in size and weight and badly where they are not. Model it by setting the shipping charge to zero and raising the margin percentage by the amount the price increase gives you, and see whether the contribution at your average order still covers the cost.
What share of customers actually add items to reach a threshold?
Nobody can tell you, and anyone quoting a specific figure is quoting someone else's catalogue. It depends on how large the gap is relative to your typical item price, on whether you have something worth adding at that price, and on how the threshold is communicated at the point where it matters. What you can do is measure it: run the threshold, look at the distribution of order values before and after rather than the average, and count the orders that now sit just above the line. That spike is the answer for your business.
Does the threshold need to be a round number?
It helps for communication and it costs a little. Rounding up to the nearest five or ten always sits on the safe side of break-even, which is why the rounding option here only ever rounds up. Rounding down to a friendlier number puts you below break-even on exactly the orders the threshold generates. If the round number below your break-even is much more attractive than the one above, the fix is to reduce the cost you are absorbing rather than to accept a loss on it.
How do I handle orders that cost far more than average to ship?
Pull them out and treat them separately, because a blended shipping figure hides them. Heavy items, bulky items and distant or hard-to-serve addresses can cost several times the average, and they clear a threshold set on the average while losing money on every one. Common answers are excluding specific products from the offer, a surcharge for particular destinations or item types, or a separate higher threshold for heavy goods. All of them are better than a single blended threshold that quietly subsidises the worst orders with the best ones.