CAC Payback Period Calculator
Months to recover customer acquisition cost
A customer who cost $300 to win and pays $50 a month at an 80% gross margin repays that cost in 7.5 months. Enter your own CAC, monthly revenue and margin, and add your churn rate: this cac payback period calculator then answers the question that decides whether payback matters at all, which is whether customers stay long enough to reach it.
How the payback period is worked out
The formula is CAC ÷ (monthly revenue × gross margin). A $300 acquisition cost against $50 a month at an 80% gross margin gives $40 of monthly gross profit and a 7.5-month payback. Until month eight, that customer has cost you more than they have returned.
Payback is a cash question, not a profitability one. It sets how long your growth spending stays underwater, which in turn sets how much capital you need to grow at a given rate. Two businesses with identical lifetime value and identical margins can have completely different funding needs purely because one recovers its acquisition cost in five months and the other in twenty.
Gross margin, never revenue
The most common way to get this wrong is to divide CAC by revenue and skip the margin. That understates payback by exactly the cost of serving the customer, and the error grows as margins fall.
| Gross margin | Monthly gross profit | Payback period |
|---|---|---|
| 40% | $20.00 | 15 months |
| 50% | $25.00 | 12 months |
| 60% | $30.00 | 10 months |
| 70% | $35.00 | 8.6 months |
| 80% | $40.00 | 7.5 months |
| 90% | $45.00 | 6.7 months |
$300 CAC, $50 monthly revenue per customer.
At $50 a month, ignoring margin entirely would suggest a six-month payback. At a 40% margin the truth is 15 months — two and a half times longer, and a completely different cash plan. Use gross margin, meaning revenue less hosting, support, payment fees and anything else that scales with each customer.
Churn decides whether payback ever happens
A payback period is only meaningful if the average customer survives it. Enter a monthly churn rate and the calculator converts it to an average lifetime of 1 ÷ churn months and compares the two directly.
| Monthly churn | Average lifetime | Lifetime gross profit | LTV : CAC | Outcome |
|---|---|---|---|---|
| 1% | 100 months | $4,000 | 13.33 | $3,700 profit per customer |
| 2% | 50 months | $2,000 | 6.67 | $1,700 profit per customer |
| 3% | 33.3 months | $1,333 | 4.44 | $1,033 profit per customer |
| 5% | 20 months | $800 | 2.67 | $500 profit per customer |
| 8% | 12.5 months | $500 | 1.67 | $200 profit per customer |
| 10% | 10 months | $400 | 1.33 | $100 profit per customer |
| 13% | 7.7 months | $308 | 1.03 | Barely breaks even |
| 15% | 6.7 months | $267 | 0.89 | Churns before repaying CAC |
$300 CAC, $50 monthly revenue, 80% gross margin — a 7.5-month payback throughout. Only the churn rate changes.
The payback period is identical in every row. What changes is whether it is ever reached. At 13% monthly churn the average customer lasts 7.7 months against a 7.5-month payback and contributes $7.69 of lifetime profit; at 15% they are gone before breaking even and every sale destroys value. Growing faster in that state makes the problem larger, not smaller.
This is why months to recover cac is worth watching monthly rather than quarterly. Payback moves when marketing efficiency changes; the verdict on whether it is survivable moves when churn changes — and the two are usually tracked by different people.
Payback by acquisition cost and revenue per customer
Business model sets payback far more than execution does. A self-serve product recovering $30 a month cannot afford enterprise-style acquisition spending, no matter how good the marketing.
| CAC | $30/mo | $50/mo | $100/mo | $250/mo |
|---|---|---|---|---|
| $100 | 4.2 | 2.5 | 1.3 | 0.5 |
| $300 | 12.5 | 7.5 | 3.8 | 1.5 |
| $600 | 25 | 15 | 7.5 | 3 |
| $1,200 | 50 | 30 | 15 | 6 |
| $3,000 | 125 | 75 | 37.5 | 15 |
Payback in months at an 80% gross margin.
Everything above roughly 24 months is in trouble regardless of lifetime value, because it requires you to fund more than two years of growth before a single cohort turns cash-positive. The bottom-left corner of that table — high acquisition cost against low revenue per customer — is where most failed subscription businesses actually died.
What counts as a good payback period
The widely used benchmarks put under 12 months as healthy for a subscription business and under 6 months as strong. They are conventions rather than laws, and they assume monthly billing. Used as a plain cac payback calculator with no churn figure entered, those two thresholds are the only judgement available — which is precisely why the churn input is worth filling in.
Two adjustments matter. Annual prepayment collapses payback dramatically, because a year of cash arrives on day one — which is the real reason so many products discount annual plans. And a business selling to enterprises can tolerate a longer payback than a self-serve one, because enterprise churn is typically much lower, so the customer is far more likely to reach the finish line.
What payback tells you that a lifetime-value ratio cannot
LTV:CAC measures total return; payback measures speed. They answer different questions and can disagree sharply. A customer worth $4,000 over eight years against a $300 CAC gives a superb 13:1 ratio — and if the payback is 30 months, growth still consumes cash for two and a half years.
Ratios are also built on a churn forecast, which for a young product is often a guess. Payback rests on this month's revenue and this month's margin, so it is the more reliable of the two early on. Use payback for cash planning and hiring decisions, and the LTV ratio to judge whether the customers are worth acquiring at all.
A planning estimate. Use your own blended CAC and cohort churn rather than headline figures.
What the payback period assumes
Monthly gross profit per customer is monthly revenue × gross margin. The payback period is CAC ÷ that figure. With churn supplied, average customer lifetime is 1 ÷ monthly churn months, lifetime gross profit is lifetime × monthly gross profit, and the LTV:CAC ratio divides that by CAC.
- Gross margin is required, not optional. Dividing CAC by revenue is the single most common error in this calculation and understates the payback by the whole cost of serving the customer.
- Churn is converted with the standard 1 ÷ churn identity, which assumes a constant monthly rate. Real churn is usually front-loaded, with new customers leaving faster than established ones, so this slightly overstates the lifetime of a young cohort.
- Monthly billing is assumed. Annual prepayment collects the full year on day one and shortens payback far more than this model shows.
- The "12 months healthy, 6 months strong" guidance is an industry convention, as is the 3:1 LTV:CAC target. Both are widely used benchmarks rather than measured thresholds, and both shift with billing model and customer segment.
- No discounting or expansion revenue. Future profit is counted at face value, and upsells or price rises within the customer's life are not modelled — so a business with strong net revenue retention will do better than this suggests.
Reviewed September 2026.
Figures reviewed . Every worked example on this page is checked against the calculator above.
CAC Payback Period Calculator: frequently asked questions
How is CAC payback period calculated?
Divide CAC by the monthly gross profit per customer, which is monthly revenue multiplied by gross margin. A $300 CAC with $50 a month at an 80% margin gives $40 of monthly profit and a 7.5-month payback.
What is a good CAC payback period?
Under 12 months is generally considered healthy for a subscription business and under 6 months is strong. Anything beyond about 24 months means funding more than two years of growth before a cohort turns cash-positive.
Should I use revenue or gross profit?
Gross profit. Dividing CAC by revenue ignores the cost of serving the customer and understates payback — at a 40% margin the true figure is 15 months where revenue alone suggests 6.
What happens if churn is higher than my payback period?
You never recover the acquisition cost. At 15% monthly churn the average customer lasts 6.7 months against a 7.5-month payback, so each new customer destroys value and growing faster makes it worse.
How do I convert monthly churn into a customer lifetime?
Average lifetime in months is 1 ÷ monthly churn rate. At 3% churn that is 33.3 months; at 10% it is 10 months. The calculator does this and compares it directly with your payback period.
Does annual billing change the payback period?
Dramatically. Collecting a year upfront means the cash arrives on day one rather than over twelve months, which is the main commercial reason annual plans are discounted so heavily.
Is CAC payback the same as LTV:CAC?
No. Payback measures how fast you get your money back; LTV:CAC measures how much you get back in total. A 13:1 ratio with a 30-month payback is still a business that consumes cash for two and a half years.
How does this differ from a CAC calculator?
A CAC calculator works out what acquiring a customer costs. This one takes that figure and answers how long it takes to earn back, which is the cash-flow question rather than the efficiency one.