Is your business model sustainable? The LTV:CAC ratio is the most important metric of the unit economics of a SaaS or a subscription business: it compares how much a customer is worth over their lifetime (LTV) with how much it costs to acquire them (CAC). The benchmark is 3:1: a customer should be worth at least three times the cost to acquire them. This calculator determines the LTV, the LTV:CAC ratio, the average customer lifetime and the CAC payback. It is the essential tool for founders, investors and growth teams.

What the LTV:CAC ratio is

The LTV:CAC ratio compares the lifetime value of a customer (LTV, Lifetime Value) with the cost to acquire them (CAC, Customer Acquisition Cost). If a customer brings you €1,600 of margin over time and costs €400 to acquire, the ratio is 4:1. It is the indicator that tells you whether your acquisition model is profitable and scalable: spending to acquire customers makes sense only if each is worth much more than they cost. It is the metric investors look at first in a SaaS.

Why the benchmark is 3:1

The established reference is a 3:1 ratio: every euro spent on acquisition should generate at least three of customer value. Below 1:1 you lose on every customer. Between 1 and 3 you acquire at a loss or with margins that are too thin. Around 3:1 the model is healthy and sustainable. Above 5:1 the model is very profitable, but it may signal that you are investing too little in growth: you could acquire more customers by spending more, accelerating expansion. The goal is not to maximize the ratio, but to find the balance.

How the LTV is calculated

The LTV (lifetime value) is how much margin a customer generates before churning. The most used formula is: LTV = average monthly revenue × gross margin / monthly churn. The average revenue (ARPA) is how much a customer pays on average per month; the gross margin is the share left after the direct costs of the service; the churn is the percentage of customers lost each month. With ARPA €100, margin 80% and churn 5%: LTV = 100 × 0.8 / 0.05 = €1,600.

How the CAC is calculated

The CAC (customer acquisition cost) is how much you spend on average to acquire a new customer: total marketing and sales costs divided by the number of customers acquired in the period. It includes advertising, sales team salaries, tools and fees. A CAC of €400 means that, on average, each new customer costs €400 across all acquisition expenses. It is the denominator of the ratio and the cost to recover with the customer's future margins.

The average customer lifetime

The average customer lifetime is how many months on average a customer stays before churning, and it is the inverse of the churn: 1 divided by the monthly churn rate. With a churn of 5% per month, the average lifetime is 20 months (1 / 0.05). It is the multiplier of the LTV: the longer customers stay, the more value they generate. Reducing the churn is the most powerful lever on the LTV: halving the churn doubles the lifetime and thus the LTV, without spending a euro more on acquisition.

The CAC payback

The CAC payback is the number of months needed to recover the acquisition cost with the customer's margins: CAC divided by the monthly contribution margin. With a CAC of €400 and a monthly margin of €80, the payback is 5 months. It is crucial for cash: an excellent LTV:CAC but with a 24-month payback strains liquidity, because you advance the cost and recover it very slowly. A payback under 12 months is generally considered healthy.

The monthly contribution margin

The monthly contribution margin per customer is the average revenue multiplied by the gross margin: how much each customer contributes per month after direct costs. With ARPA €100 and margin 80%, it is €80 per month. It is the "engine" of the LTV (LTV = monthly margin × lifetime) and of the CAC payback (payback = CAC / monthly margin). Increasing it — by raising prices or improving the margin — improves the LTV, ratio and payback at the same time.

How the calculator works

Enter the average monthly revenue per customer (ARPA), the gross margin, the monthly churn and the CAC. The calculator determines the LTV, the LTV:CAC ratio, the average customer lifetime, the CAC payback and the monthly contribution margin. The verdict tells you whether your unit economics are critical, below threshold, healthy or very profitable. It is the quickest way to understand whether your growth model is sustainable and where to act.

The values you need

The average monthly revenue (ARPA) is the revenue divided by the number of active customers, per month. The gross margin is the percentage of revenue left after the direct costs of delivering the service (hosting, support, licenses). The monthly churn is the percentage of customers lost each month. The CAC is the average cost to acquire a customer. Use consistent data from the same period for a reliable result.

Interpreting the LTV:CAC ratio

How to read the ratio:

3:1 is the classic SaaS benchmark: customer value at least triple the acquisition cost.

Effect of churn on the LTV

The churn determines the customer lifetime and thus the LTV (at the same ARPA €100 and margin 80%):

Reducing the churn is the most powerful lever: halving it doubles the lifetime and the LTV without spending more on acquisition.

Example: same CAC, different LTV

With a CAC of €400, how the ratio changes as the LTV varies:

At the same acquisition cost, increasing the LTV (prices, margin, retention) directly improves the ratio.

How to improve the ratio

Two levers improve the LTV:CAC ratio. On the LTV side: reduce the churn (retention, onboarding, perceived value), increase the ARPA (upsell, cross-sell, price increases) and improve the gross margin. On the CAC side: more efficient acquisition channels, better targeting, referrals and organic growth, optimization of the sales funnel. Beware of false savings: cutting the CAC too much can slow growth. The goal is sustainable profitability, not the maximum ratio.

What the calculation does not consider

The calculator uses a simplified model with constant churn and ARPA: in reality the churn can vary over time and the ARPA grow with expansion (upsell). It does not consider the time value of money (a margin collected in two years is worth less than one today; more refined models discount the LTV). It does not distinguish customer segments (the average ratio can hide very different segments). It does not include retention costs. It is a managerial estimate to orient decisions, not a complete financial model.

Common mistakes

• Using revenue instead of margin in the LTV (overestimates the customer value).
• Underestimating the CAC by forgetting salaries, tools and fees.
• Ignoring the CAC payback: a good ratio with a long payback strains cash.
• Using an annual churn instead of the monthly one (or vice versa) without converting.
• Aiming for a very high ratio: above 5:1 you may be under-investing in growth.

How to use the calculator

Enter the average revenue, margin, churn and CAC. Read the LTV, the ratio, the customer lifetime, the payback and the monthly margin. Compare the ratio with the 3:1 benchmark. Try reducing the churn or increasing the ARPA to see how the LTV improves, or reducing the CAC to see the effect on the ratio. It is the quickest way to assess the sustainability of your model and identify the lever to act on.

Practical example

Your SaaS has an average revenue of €100 per month per customer, a gross margin of 80%, a monthly churn of 5% and a CAC of €400. The result: an LTV of €1,600, an LTV:CAC ratio of 4:1, an average lifetime of 20 months, a CAC payback of 5 months and a contribution margin of €80 per month, with the verdict "healthy: ideal ratio, in line with the 3:1 benchmark". Your unit economics hold: each customer is worth four times the acquisition cost. Enter your numbers for your real situation. The calculation uses a simplified model with constant churn and ARPA and does not discount the time value of money. It is an informational managerial estimate, not financial advice.

Frequently asked questions

What is the LTV:CAC ratio?

It is the comparison between the lifetime value of a customer (LTV) and the cost to acquire them (CAC). It tells you whether the acquisition model is profitable: a customer should be worth much more than they cost to acquire. The benchmark is 3:1.

Why is the benchmark 3:1?

Because a 3:1 ratio indicates a healthy model: every euro spent on acquisition generates three euros of customer value, also covering operating costs and leaving margin. Below 3:1 profitability is thin; above 5:1 you may under-invest in growth.

How is the LTV calculated?

The most used formula is: LTV = average monthly revenue × gross margin / monthly churn. With ARPA €100, margin 80% and churn 5%: LTV = 100 × 0.8 / 0.05 = €1,600. It is the total margin a customer generates before churning.

How is the CAC calculated?

The CAC (customer acquisition cost) is the total marketing and sales costs divided by the number of customers acquired in the period. It includes advertising, sales team salaries, tools and fees. Underestimating it distorts the ratio.

What is the CAC payback?

It is the number of months to recover the CAC with the customer's margins: CAC divided by the monthly contribution margin. With a CAC of €400 and a monthly margin of €80, the payback is 5 months. Under 12 months is generally healthy; a long payback strains cash.

Why use margin and not revenue in the LTV?

Because the real value of a customer is the margin they leave, not the gross revenue. Using revenue overestimates the LTV by ignoring the direct costs of delivering the service. The correct LTV uses the gross margin.

How does churn affect the LTV?

The churn determines the customer lifetime (lifetime = 1/churn), which multiplies the LTV. With a churn of 5% the lifetime is 20 months; with a churn of 10% it drops to 10 months, halving the LTV. Reducing the churn is the most powerful lever on the LTV.

Is a very high ratio always positive?

Not necessarily. Above 5:1 the model is very profitable, but it may indicate you are investing too little in acquisition: you could grow faster by spending more. The goal is sustainable growth, not the maximum ratio.

What is the difference between LTV:CAC and CAC payback?

The LTV:CAC ratio measures the overall profitability (how much a customer is worth vs how much they cost). The CAC payback measures the speed of recovery (in how many months you recoup the cost). A good ratio with a long payback can still create cash strain.

Does it apply only to SaaS?

It was born in the SaaS world but applies to any recurring or subscription business: e-commerce with loyal customers, gyms, services, digital publishing. Wherever there are customers paying over time and a cost to acquire them, the LTV:CAC ratio is useful.

Does the calculation discount the time value of money?

No, it uses a simplified model with constant churn and ARPA and does not discount future flows. More refined models discount the LTV to reflect that a margin collected in two years is worth less than one today. For quick estimates the simple model is sufficient.

Does it work for any country and currency?

Yes, the calculation is universal and uses the values and currency you enter. LTV, CAC and their ratio are standard unit economics concepts valid everywhere; the ratio is a pure number, independent of the currency.

Updated July 2026