CAC Payback Calculator
From your ad spend, funnel, price and churn: your CAC, LTV, LTV:CAC and the months until a customer pays you back.
From ad spend to payback
The model follows a paid funnel from spend to paying customer, then values each customer from your price, margin and churn.
| Number | How it is worked out | What it tells you |
|---|---|---|
| CAC | Acquisition spend ÷ new customers | What one new customer costs. Add salaries and tools for the fully loaded number. |
| Revenue per customer | Seats × weighted plan price, or your average price per customer | What each customer pays a month. |
| Customer lifespan | 1 ÷ monthly churn, up to the LTV cap | At 5% monthly churn the average customer stays 20 months. |
| Revenue lifetime | 1 ÷ (churn − expansion), up to the LTV cap | How long a customer's revenue lasts, upsells counted. |
| LTV | Revenue per customer × gross margin × revenue lifetime | Gross profit a customer brings before they leave. |
| LTV:CAC | LTV ÷ CAC | Profit back for each dollar spent to win a customer. |
| CAC payback | CAC ÷ (revenue per customer × gross margin) | Months until a customer pays back what they cost. |
| Net revenue retention | (1 − churn + expansion)12 | Revenue kept from a group of customers after a year. |
| Magic number | New MRR × 12 ÷ monthly acquisition spend | New ARR each dollar of spend buys, before churn. |
| Max CAC | LTV ÷ 3 | The most a customer may cost to hold a 3:1 ratio. |
Rules of thumb, not laws
Common SaaS benchmarks. Your stage, buyers and cash change what good looks like.
| Number | Healthy | Why |
|---|---|---|
| LTV:CAC | 3:1 to 6:1 | Below 1:1 every customer loses money. Far above 6:1 often means you spend too little on growth. |
| CAC payback | 12 months or less | Longer payback ties up cash. Annual contracts can carry more. |
| Net revenue retention | 100% or more | Above 100% your customers grow revenue on their own. |
| Magic number | 0.75 or more | Below 0.5 spend is not turning into recurring revenue. |
| Gross margin | 70% to 85% | A low margin shrinks LTV and stretches payback. |
What we do with your max CAC
Your max CAC is the most a new customer may cost you. These are the three ways we use it.
A ceiling before the first ad
LTV ÷ 3 is the most a customer may cost. That number sets the test budget and the bids.
Stop rules per ad
The calculator also shows the most you can pay per visitor, lead and SQL. An ad that costs more stops, so a bad ad costs little.
Real costs every Monday
Ad platform costs and your sign-ups go into the same math each week. The plan moves with them.
We run this math for you before the first ad, then every Monday with real costs, in the Growth Strategy™.
More Growth Strategy™ tools: Channel FinderARR CalculatorICP Builder
Frequently asked questions
How is CAC worked out?
Acquisition spend for a period divided by the new customers won in it. Ad spend alone gives paid CAC. Add salaries, tools and agency fees for the fully loaded CAC.
How is LTV worked out here?
Monthly revenue per customer × gross margin × revenue lifetime, where revenue lifetime is 1 ÷ (monthly churn − monthly expansion). Gross margin keeps hosting and support costs in the number.
Why is LTV capped?
With very low churn, or expansion above churn, the formula says customers pay for decades. The cap (60 months by default) keeps LTV to a time you can plan for. Set it to 0 to remove it.
What is a good LTV:CAC and payback?
3:1 is the most used rule of thumb for LTV:CAC, and 12 months or less for payback. Below 1:1 you lose money on every customer.
Is what I enter saved?
No. The calculator runs in your browser and sends nothing, to us or to anyone else. Your inputs stay in the page address after the # sign, which a browser does not send to a server, so you can bookmark or share a scenario.
Let's bring in the customers, together.
As a first step, book a free 30-minute strategy call with Ovidiu.
You leave with a plan: which channel, how much, what first.