Promotion math
Coupon affiliate leakage.
Enter monthly orders, how many use an affiliate code, and the share who were already buying. See the cost of discount plus commission on those orders, net profit, and the leakage at which the channel stops paying.
Net profit = incremental orders x profit per coupon order - leaked orders x (margin on a normal order - profit per coupon order). The example below nets $2,600 a month and stays profitable up to 53% leakage.
Your numbers
Result
Worked example
A store takes 2,000 orders a month and 25% use an affiliate coupon, so 500 coupon orders. It estimates that 40% of them, 200 orders, were already going to buy, for example shoppers who searched for a code at checkout. At an $80.00 order, a 15% discount, a 10% commission on the discounted price and a 50% margin, a coupon order earns $80.00 x (0.50 - 0.15) - 10% x $80.00 x 0.85 = $21.20. A leaked order would have earned $40.00 without the code, so each one costs $18.80. Leakage costs $3,760 a month, 300 incremental orders earn $6,360, and the channel nets $2,600. It stops paying at 53% leakage.
How it works
Profit per coupon order = order value x (margin - discount) - commission x order value x (1 - discount). Both the discount and the commission come out of the margin; the commission is charged on what the shopper actually pays.
Cost per leaked order = full-price margin - profit per coupon order. A leaked order was already yours, so everything you gave away on it is pure loss.
Net profit = incremental orders x profit per coupon order - leaked orders x cost per leaked order. Incremental orders would not have happened without the code, so they earn the full coupon-order profit.
Break-even leakage = profit per coupon order / full-price margin per order. If real leakage is above that, the channel loses money even though sales are tracked as "affiliate revenue".
To estimate leakage, compare the code's orders with shoppers who were already in the cart, or on your list, before the code was used. This tool does not scrape coupon sites or measure anything for you; the share you enter is an estimate. If affiliates promote your codes, they should disclose that they earn a commission.
Sources
Retrieved 2026-10. The formulas are arithmetic on your inputs; the sources below are the rules and standards this page refers to.
- FTC Guides Concerning the Use of Endorsements and Testimonials in Advertising, 16 CFR Part 255: section 255.5 says a connection that might materially affect the credibility of an endorsement, such as payment or free or discounted products, must be disclosed clearly and conspicuously.
Everything runs in your browser. Nothing you type is sent or stored. This is a planning aid, not legal or accounting advice.
FAQ
What is coupon code leakage?
It is the share of coupon orders that would have happened anyway. Shoppers who were about to pay full price search for a code, find one from an affiliate site, and you pay a discount and a commission for a sale you already had.
How do I estimate how many were going to buy anyway?
Compare the share of coupon users who arrive straight to the cart, or who had a session before, with total orders. Even a rough test, such as pausing a code for a week, gives you a number to enter.
Is the commission paid on the discounted price?
It depends on your affiliate terms. This tool charges the commission on the amount the shopper pays. If your network pays on the pre-discount price, use a slightly higher percentage.
Can I stop leakage without ending the programme?
Common fixes are unique single-use codes for partners, a "last click wins" rule that excludes direct traffic, and keeping the code out of the checkout box so shoppers do not go looking for one.