How do you calculate CAC payback period?

Fully loaded acquisition cost per customer, divided by monthly gross margin per customer. The answer is in months. Using revenue instead of gross margin understates it, often by half.

What is a good CAC payback period?

Shorter is better and the threshold depends on how you are funded. The widely quoted 12 months is a convention, not a finding — a business with 18 months of runway and one with five years should not be judged against the same number.

Why use payback instead of LTV:CAC?

LTV:CAC asks whether acquisition eventually pays. Payback asks whether you can afford the wait. A 5:1 ratio recovered over four years is worse for a cash-constrained business than 3:1 recovered in nine months.

Should expansion revenue count toward payback?

Only if you also count the cost of producing it. Counting expansion margin against new-customer acquisition cost flatters the number, because the success and account management effort behind it is left out.

CAC Payback Period

How long it takes for a customer's gross profit to repay the cost of acquiring them. The bridge between sales efficiency and cash flow.

The calculation

Fully loaded acquisition cost per customer, divided by gross margin per customer per month. The result is the number of months before that customer has repaid what it cost to win them.

Gross margin, not revenue

Revenue-based payback counts money that leaves again as hosting, support and success cost. In a service-heavy business it can halve the apparent payback period. If you cannot get gross margin per customer, that is the finding to act on first.

Why it is the more useful of the two ratios

LTV:CAC and payback answer different questions. The ratio asks whether acquisition is profitable in the end; payback asks how long your cash is tied up getting there. For anything other than an unconstrained balance sheet, the second question binds first.

A business can have an excellent ratio and still fail, if every customer takes three years to repay and growth is funded from cash flow. Payback makes that visible where the ratio hides it.

Computing it defensibly

Use fully loaded acquisition cost — salaries, commission, benefits, tooling, agencies and programme spend — not media spend alone.
Offset the cost period by your median sales cycle, so spend is matched to the customers it plausibly produced.
Use gross margin per month, and state what is in cost of service.
Compute per segment and per channel. A blended figure averages motions with genuinely different economics.
Report it beside LTV:CAC rather than instead of it. Together they say whether acquisition pays and whether you can wait.

Where it misleads

It ignores everything after payback, so a business with short payback and heavy churn can look healthier than one with longer payback and durable customers.
Discounting the first year shortens apparent payback while lowering lifetime value — the metric improves as the economics worsen.
Annual prepayment changes cash timing without changing the underlying economics; state whether you are measuring cash or margin.

RELATED TERMS

LTV:CAC Ratio

Lifetime value divided by acquisition cost. Whether a customer returns more than they cost to win.

Magic Number

A sales efficiency measure comparing new recurring revenue produced to the sales and marketing spend that produced it.

Customer Acquisition Cost (CAC)

The fully loaded cost of acquiring one new customer: sales and marketing spend for a period divided by new customers acquired from it.

COMMON QUESTIONS

How do you calculate CAC payback period?: Fully loaded acquisition cost per customer, divided by monthly gross margin per customer. The answer is in months. Using revenue instead of gross margin understates it, often by half.
What is a good CAC payback period?: Shorter is better and the threshold depends on how you are funded. The widely quoted 12 months is a convention, not a finding — a business with 18 months of runway and one with five years should not be judged against the same number.
Why use payback instead of LTV:CAC?: LTV:CAC asks whether acquisition eventually pays. Payback asks whether you can afford the wait. A 5:1 ratio recovered over four years is worse for a cash-constrained business than 3:1 recovered in nine months.
Should expansion revenue count toward payback?: Only if you also count the cost of producing it. Counting expansion margin against new-customer acquisition cost flatters the number, because the success and account management effort behind it is left out.