CAC alone is a dollar figure and LTV is a lifetime total — payback period answers the more immediate cash-flow question a SaaS business actually manages against.
How it works
Monthly gross margin per customer (revenue times gross margin percentage) is divided into CAC to find how many months of that margin it takes to recover the acquisition cost.
What this does not include
This uses a flat monthly revenue figure — a business with expansion revenue (customers who grow their spend over time) would recover CAC faster than this simple calculation shows, since later months often generate more margin than the first.
How to use this calculator
- Enter CAC, monthly recurring revenue per customer, and gross margin.
A worked example
A $1,200 customer acquisition cost, $100 monthly revenue per customer, 80% gross margin: monthly gross margin per customer = 100 × 0.80 = $80, payback period = 1,200 ÷ 80 = 15 months.
What the variables mean
| Variable | Meaning |
|---|---|
| CAC | Cost to acquire one customer |
| Monthly revenue per customer | Average monthly revenue generated per customer |
| Gross margin % | Percentage of revenue retained after direct costs |
Edge cases worth knowing
This uses gross margin, not gross revenue, as the payback measure. Only the profitable portion of revenue actually pays back the acquisition cost — using raw revenue instead of margin would understate how long payback genuinely takes.
Zero gross margin makes payback infinite — a customer generating no profit margin never actually recoups the acquisition cost, so the calculator declines to show a result.
Frequently asked questions
What’s considered a good CAC payback period?
Under 12 months is commonly cited as healthy for SaaS businesses, though the right benchmark varies by industry, growth stage, and how the business is funded.
Why use gross margin instead of full revenue?
Because the cost of actually serving a customer (hosting, support) has to be covered before any revenue counts toward recovering CAC — using full revenue would overstate how fast CAC is actually recovered.
How does this relate to LTV:CAC ratio?
They’re complementary — payback period measures how fast CAC is recovered; the LTV:CAC ratio (this site’s separate calculator) measures the total return over a customer’s full lifetime.
