Free shipping threshold: how to calculate it from your margin and average order value

«Free shipping on orders over €50.» Many stores choose the figure because the competition uses a similar one or because it sounds round. But that number decides how much margin you give away on each order and how much you push the customer to add something else. It can be calculated, and all you need is a spreadsheet and your store's data.

The data you need

• The real shipping cost per order, not the rate you charge: what the carrier invoices you plus packaging. Ideally by zone (mainland, islands) and by weight band.
• Average gross margin on what you sell, as a percentage of the price excluding VAT.
• Average order value and, above all, how your orders are distributed by amount: how many are under €30, between €30 and €40, and so on.
• What you currently charge for shipping, if anything.

The distribution matters more than the average. Two stores with the same average order value may have, in one case, most orders just below the threshold and, in the other, a very spread-out distribution, and they will react very differently.

The basic calculation

When an order goes up to the threshold to avoid paying for shipping, you stop charging for delivery and have to pay for it yourself. For it to be worth it, the margin on what the customer adds has to cover that cost.

The minimum additional sale is: shipping cost ÷ gross margin.

An example with round numbers, just to show the mechanism: if shipping costs you €6 and your gross margin is 40%, you need the customer to add €15 of product to pay for shipping with the margin from that additional sale. If your average order value is around €40, a threshold of about €55 asks the average customer for exactly what is needed. A €45 threshold does not cover it; an €80 one is so far away that many customers will not even try.

The forgotten cost: orders that were already above it

If you used to charge for shipping on every order and now give it away above the threshold, customers who were already buying above that figure stop paying for delivery without adding anything. That is a new cost, with no additional sale to offset it.

That is why the full calculation is: margin on the sales added by the orders that move up, minus the shipping you stop charging on those that were already above. If the result is negative with reasonable assumptions, the threshold is too low.

Different thresholds for different cases

• By zone. Shipping to the Balearic Islands, the Canary Islands, Ceuta or Melilla costs more. A different threshold is common, or free shipping on the mainland only, stated clearly.
• By size. Bulky or heavy products can be excluded, or have their own threshold.
• By carrier. Free on standard shipping, paid on express.
• For specific customers. A group of trade or repeat customers can have a different threshold.

PrestaShop includes free shipping above an amount out of the box in the shipping preferences, and each carrier's price ranges let you fine-tune by zone. For finer rules, use cart rules.

Communicating it so it works

A threshold the customer does not see raises no order values. What works:

• A message in the cart showing what is missing: «Add €8.40 more for free shipping».
• The threshold on the product page and in the header, with its conditions (zones, carrier).
• No small print that only appears at the last step.

Products to complete the cart

If the customer is €8 short of free shipping, the best help is to show them products at that price that make sense with what they already have: spare parts, consumables, accessories, small sizes. Even better if they have a good margin and sell regularly. The worst thing is to leave them searching on their own: they end up adding something they later return or simply leave.

An offer in the cart or at checkout, conditional on the amount being below the threshold, does this job without getting in the way of those who have already reached it.

How to measure whether the threshold works

Compare several weeks before and after the change, with no campaigns in between to distort it:

• Average order value and distribution of orders by amount. If it works, you will see a cluster just above the threshold.
• Margin per order after paying for shipping, not just revenue.
• Cart conversion rate.
• Returns of products added to complete the cart.

If order value goes up but margin per order goes down, the threshold is giving away more than it brings in.

The threshold as a perk, not just for shipping

The same mechanism works for other perks: above a certain amount, gift wrapping, free returns or free shipping protection. These are incentives that cost less than delivery and that customers also value.

Checklist

• Real shipping cost by zone and weight.
• Minimum additional sale = shipping cost ÷ gross margin.
• Cost of orders that were already above the threshold.
• Thresholds by zone or size where needed.
• An «add €X more» message in the cart.
• Products to complete the cart close to the difference.
• Measuring margin per order, not just order value.

How to solve it in PrestaShop

RKR Buy More Pro shows an offer in the cart, at shipping or at payment that the customer adds with one click, and you set its conditions by minimum and maximum cart amount, by number of items or by the products and categories it contains: you can show an add-on only to those below the threshold. If the customer removes what justified the offer, the discounted line is removed automatically, and the A/B test tells you which offer converts best. RKR Shipping Protection offers optional shipping protection with its own fee and lets you make it free above the amount you choose, with rules per carrier: another way to give value to those who exceed the threshold.