CAC Payback Calculator

See how many months it takes to earn back what a customer cost, using your store's own repeat-purchase rate, not a SaaS subscription model.

Your numbers

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Customer acquisition cost (CAC)

Average order value

Contribution margin per order

Order value minus product cost, shipping and payment fees, before ad spend.

Share of customers who order again

Within your usual reorder window, from your store's own repeat customer rate.

Average days between orders

For customers who do come back, from your order history.

days

Your result · updates as you type

Expected time to pay back CAC

4.2 months

The first order covers $26.00 of the $45.00 CAC. At a 35% repeat rate, the rest arrives gradually as customers reorder, not all at once.

Contribution from order 1: $26.00
Still owed after order 1: $19.00
Expected reorders to break even: 2.1

This spreads CAC across a repeat-purchase curve, not a fixed monthly subscription like SaaS payback. A higher repeat rate shortens payback more than a higher AOV does, because it raises the odds every future order actually happens.

Expected cumulative contribution per customer

Order 1

$26.00

Order 2

$35.10

Order 3

$44.20

Order 4

$53.30

Breakdown

CAC: $45.00
Contribution from order 1: −$26.00
Still owed after order 1: $19.00
Expected contribution per reorder cycle (35% × $26.00): $9.10
Days between orders: 60 days
Expected time to pay back CAC: 4.2 months

Why ecommerce payback isn't a SaaS formula

SaaS payback calculators assume a fixed monthly subscription arrives like clockwork. Ecommerce doesn't work that way: a customer might reorder in three weeks, three months, or never. This calculator spreads CAC across an expected repeat-purchase curve instead, using your store's own repeat rate.

Contribution from order 1 = order value × margin Contribution per reorder cycle = contribution from order 1 × repeat rate Months to pay back = (CAC − order 1 contribution) ÷ contribution per cycle × days between orders ÷ 30

Example: the default numbers

CAC: $45
Order value × margin (order 1): $65 × 40% = $26
Still owed after order 1: $45 − $26 = $19
Repeat rate × order 1 contribution: 35% × $26 = $9.10 per cycle

It takes 19 ÷ 9.10 = 2.09 expected reorder cycles to clear the rest. At 60 days between orders, that's about 4.2 months to pay back this customer's CAC.

Reading the result

Under 6 months is comfortable for most stores funding ads from cash flow.
Over 12 months ties up cash for a long time. Either the first order needs to cover more of CAC, or the repeat rate needs to improve.
Repeat rate moves payback faster than order value does, because it changes the odds that any given future order happens at all.

If the first order alone covers CAC, the calculator says so directly. That's the strongest position: profitable even if a customer never returns.

Questions people ask

What is CAC payback period?

How long it takes for a customer's contribution margin to add up to what it cost to acquire them. Shorter is better, because your cash isn't tied up as long.

Why doesn't this use monthly recurring revenue like SaaS payback calculators?

Ecommerce customers don't pay on a fixed schedule. This tool discounts future orders by your repeat purchase rate instead of assuming every customer buys every month.

What if my repeat rate is 0%?

Then only the first order ever contributes to paying back CAC. Improving repeat purchases (email flows, subscriptions, loyalty) is usually a faster fix than cutting CAC.

How is this different from LTV:CAC?

LTV:CAC gives you a ratio for the whole customer lifetime. This tool gives you a timeline: how long the cash stays tied up before that value shows up.

Last reviewed 30 September 2026.