Free Gift Margin Math, With Worked Examples

A free gift is never free to you. The only question is whether the extra money it pulls out of shoppers is larger than what it costs you to hand it over. This page turns that question into one free gift margin formula with four inputs, then runs it three times for three very different catalogs so you can see where a gift pays and where it quietly loses money. Every number in the tables is an assumption stated in the text, not a benchmark, so replace them with your own before you trust a result.

The one formula

Start with the orders that qualify for the gift. Some of them spent more because of the offer: they were below the threshold and added items to reach it, or they would not have ordered at all. The rest would have crossed the threshold anyway, and for them the gift is pure cost.

Define four inputs and one unknown:

• G is the landed cost of one gift, in dollars (explained in the next section).
• E is the extra spend per order from shoppers the offer actually moved, in dollars.
• m is your gross margin on that extra spend, as a share of the price (a 40 percent margin is 0.40).
• f is the percentage payment fee on that extra spend (a 3 percent fee is 0.03).
• p is the unknown: the share of gift recipients who were moved by the offer.

Per qualifying order, the offer earns p × E × (m − f) and costs G. Break-even is where the two are equal:

p at break-even = G ÷ (E × (m − f))

Read it as a hurdle. If the result is 0.40, then 40 percent of the people who receive the gift have to be shoppers who spent more because of it. If the result is above 1.00, the gift loses money even when every single recipient was moved, because each moved order earns less than the gift costs. That second case is more common than most banners suggest.

The fixed per-transaction part of a payment fee is left out on purpose. A moved order that already existed pays that fee either way. A brand-new order does pay it, so if many of your recipients are brand-new orders, subtract that fixed amount from E × (m − f) as well.

Landed cost of a gift

G has more parts than the invoice price of the item. Add these, per unit:

1. Unit cost from your supplier, including inbound freight and duty if you pay it.
2. Packaging and inserts, such as a sleeve, a card or a sample pouch.
3. Handling, which is the extra seconds a packer spends finding and adding the item. If you pay a fulfillment partner by the pick, this is a line on the invoice.
4. Added postage, which is the change in shipping cost caused by the gift's weight and size.

The fourth item is the one most gift math skips, and it deserves its own section.

The shipping weight you forgot

Postage is stepped, not smooth. USPS Notice 123, the price list effective October 4, 2026, shows commercial USPS Ground Advantage with weight rows at 4 ounces, 8 ounces, 12 ounces and 15.999 ounces, and then whole-pound rows from 1 through 70 pounds, with columns for the zone groups. A parcel that weighs 15 ounces without the gift sits in the last ounce row. Add a 3 ounce gift and the parcel passes 1 pound, so it is priced in the next row up, and every further whole pound is another step. The price jump depends on the zone, so the same gift costs more to send across the country than across town. This page does not quote the prices, because Notice 123 changes; look up your own rows in the notice or in your postage software.

To put a number on it, weigh a typical order with and without the gift on a postal scale, check both weights against the rows for your two most common zones, and use the difference as the added postage. Do the same for a dimensional change if your carrier prices by size. If the gift never changes the row, the added postage is zero and you can say so. If it does, the postage can cost more than the gift itself.

Contribution margin on the extra spend

Use the margin on what the shopper added, not your store average. A store whose average margin is 50 percent might have a 65 percent margin on accessories and 30 percent on the hero product, and the shopper who adds a little to reach a threshold usually adds the accessory. Compute m from the specific items that people add to cart to reach the threshold. If you cannot tell, use the lower of your two likely numbers.

The same logic applies to discounts. A gift that comes with a percentage discount on the order changes m directly; our break-even discount page has the matching formula for that case.

Three worked examples

All three examples use one gift per qualifying order, a payment fee of 3 percent as a stand-in for the percentage part of your own rate, and a cart threshold chosen above the current average order. Every input below is an assumption.

Example A: a low-margin catalog. Gross margin on the extra items is 30 percent. The gift is a branded pouch with a unit cost of 4.00 dollars, 0.50 dollars of packaging and 1.10 dollars of added postage because it tips the parcel into the next weight row, so G = 5.60 dollars. Moved shoppers add 20 dollars on average.

Example B: a mid-margin catalog. Gross margin is 50 percent. The gift costs 3.50 dollars, plus 0.50 for packaging and 0.80 for added postage, so G = 4.80 dollars. Moved shoppers add 20 dollars.

Example C: a high-margin catalog. Gross margin is 70 percent. The gift is a small sample with a unit cost of 3.00 dollars, 0.50 for packaging and 0.60 for added postage, so G = 4.10 dollars. Moved shoppers add 25 dollars.

Check the arithmetic on Example B: 20 × (0.50 − 0.03) = 9.40, and 4.80 ÷ 9.40 = 0.51. Half of the people who get the gift have to be people it moved.

What the table says. In the low-margin catalog the hurdle is 1.04, so the gift loses money even if every recipient was moved. The remedy is not a better banner. It is a cheaper or lighter gift, a higher threshold that raises E, or a different tool altogether, such as a small percentage off, which costs nothing when nobody qualifies. In the mid-margin case the gift works if about half of recipients behave differently because of it, which is plausible when the threshold sits just above your current average order and not far above it. In the high-margin catalog a quarter of recipients is enough, which is why samples and minis do well for beauty and supplements.

Use the table in reverse as well. If you suspect that only one recipient in five is truly moved, the gift pays only if G ÷ (E × (m − f)) is 0.20 or less. For Example C that means a landed cost of 3.35 dollars or less (0.20 × 16.75), so trimming 0.75 dollars from the gift turns a marginal offer into a safe one.

Pricing the required purchase

Do not close a weak gap by quietly raising the price of the item that must be bought. The FTC's guide on the word "free" (16 CFR 251.1) says shoppers have a right to believe the seller will not recover the cost of the free item by marking up the price of the article that must be purchased. The same section says the offer is based on a regular price, which it defines as the price at which the seller has openly and actively sold the product in the most recent and regular course of business for a reasonably substantial period, meaning a 30-day period. If the math above does not work at today's prices, change the gift, the threshold or the tool, not the base price. This is not legal advice.

Copy this into a spreadsheet

Set up one row per offer and one column per input.

1. Column A: gift name. Column B: unit cost. Column C: packaging. Column D: handling per order. Column E: added postage per order from your weighing test. Column F: G, the sum of B through E.
2. Column G: E, the extra spend of a moved order. Take it from orders that landed within a few dollars above the threshold.
3. Column H: m, the margin of the items those orders added. Column I: f, your percentage payment fee. Your card rate depends on your plan and payment provider, so read it from your own payment settings or statements instead of guessing.
4. Column J: earned per moved order, written as the formula G × (H − I), where G, H and I are spreadsheet columns, not the formula variables.
5. Column K: break-even share, written as the formula F ÷ J. Format it as a percentage.
6. Column L: your honest estimate of the share of recipients who were moved, from a comparison of average order value before and after, and column M: the verdict, written as an IF formula that says "pays" when L is above K.

When K is above 100 percent, put the row in a "rework" tab. When it is below 30 percent, you have room to raise the gift's perceived value. Between those, run it for a defined window with a stock cap and measure.

Build it, then cap the cost

Once the row says the offer pays, build it from the Spend X, get a gift template in Freebies Engine by Log Studio Lab, which is described as "Shoppers who reach a cart value get a gift added automatically." Set the threshold from your spreadsheet, pick the gift whose G you calculated, and set a stock cap or end date so the cost cannot run past the plan. On Shopify's own side, the Buy X get Y discount shows a free item as sold out when the free product's inventory reaches zero, which makes a limited gift stock a natural cap. For the thresholds themselves, see our guide to free shipping thresholds, and for the strictest check before a big weekend, see the Black Friday and Cyber Monday offer plan. For the basics of the offer type, start with what a free gift with purchase is.

This is a modeling aid, not a forecast. The share of recipients who are moved is the one input you cannot know in advance, so treat the first run as a measurement and the second as the decision.