Sales Funnel LTV to CAC Ratio Formula
Learn how the Sales Funnel LTV to CAC Ratio Calculator estimates customer lifetime value, acquisition cost, and the LTV to CAC ratio.
This page explains the core math behind the Sales Funnel LTV to CAC Ratio Calculator. The formula helps estimate whether the value created by a customer is large enough relative to the cost required to acquire that customer.
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LTV to CAC Ratio
Where:
Divide estimated lifetime value per customer by the cost to acquire one customer to see how much value is generated for each unit of acquisition cost.
Variables Explained
| Variable | What It Means | Unit |
|---|---|---|
| L - Monthly leads | The number of leads entering the funnel in a typical month. | number |
| CR - Lead-to-customer conversion rate | The percentage of leads that become paying customers. | percent |
| ARPC - Average monthly revenue per customer | The average monthly revenue produced by one active customer. | currency |
| GM - Gross margin | The percentage of revenue retained after direct costs. | percent |
| Churn - Monthly churn rate | The percentage of customers lost in a typical month. | percent |
| S - Monthly sales and marketing spend | The total monthly spend used to acquire customers. | currency |
| NC - New customers | The estimated number of new customers acquired in the month. | number |
| Life - Customer lifetime | The estimated average customer lifespan based on churn. | months |
| GPPM - Gross profit per customer per month | The gross profit contribution generated by one customer each month. | currency |
| LTV - Customer lifetime value | Estimated gross profit contribution from a customer over their expected lifetime. | currency |
| CAC - Customer acquisition cost | Estimated cost to acquire one new customer. | currency |
Step-by-Step Calculation
Estimate new customers
Convert the lead-to-customer rate to a decimal and multiply it by monthly leads to estimate how many customers are acquired.
NC = L * (CR / 100)
Estimate customer lifetime
Use the reciprocal of monthly churn to estimate the average customer lifetime in months.
Life = 1 / (Churn / 100)
Estimate gross profit per customer per month
Multiply average monthly revenue per customer by gross margin to estimate monthly gross profit contribution.
GPPM = ARPC * (GM / 100)
Calculate customer lifetime value
Multiply monthly gross profit contribution by expected customer lifetime to estimate lifetime value.
LTV = GPPM * Life
Calculate customer acquisition cost
Divide total monthly sales and marketing spend by the number of new customers acquired in the same month.
CAC = S / NC
Calculate the ratio
Divide lifetime value by acquisition cost to estimate how efficiently the funnel turns spend into long-term customer value.
LTV to CAC Ratio = LTV / CAC
Example: Recurring revenue funnel
Estimate new customers
1,000 × 0.05
50 customers
Estimate customer lifetime
1 ÷ 0.04
25 months
Estimate gross profit per customer per month
$100 × 0.80
$80
Calculate lifetime value
$80 × 25
$2,000
Calculate customer acquisition cost
$5,000 ÷ 50
$100
Calculate LTV to CAC ratio
$2,000 ÷ $100
20.00:1
Final Result
Estimated LTV to CAC ratio: 20.00:1, with LTV of $2,000 and CAC of $100.
Assumptions
- ✓Customer lifetime is estimated as the reciprocal of monthly churn.
- ✓Average revenue, gross margin, and churn are assumed to stay reasonably stable over time.
- ✓Monthly sales and marketing spend is assumed to relate to the customers acquired in that same period.
- ✓Lifetime value is based on gross profit contribution rather than revenue alone.
- ✓The business model has recurring or repeat customer value, not just a single one-time purchase.
Limitations
- !The churn-based lifetime estimate is a simplification and may not reflect real retention curves.
- !Results can be misleading if acquisition spend and customer conversions occur in different months.
- !The formula does not include discount rate, cash flow timing, refunds, or expansion revenue.
- !Seasonality, cohort differences, and channel-level performance are not captured in the basic model.
- !Very low churn rates can produce unusually large lifetime estimates that may not be realistic.
Common Mistakes to Avoid
Using revenue instead of gross profit when estimating lifetime value.
Comparing one month of spend against customers generated by a much longer sales cycle.
Entering churn as an annual percentage when the calculator expects monthly churn.
Including all leads even when many are unqualified or outside the real acquisition funnel.
Ignoring that conversion rates and churn can vary significantly across channels or customer segments.
Related Formulas
Frequently Asked Questions
What is the basic LTV to CAC ratio formula?
The basic formula is LTV divided by CAC. In this calculator, LTV is estimated from monthly gross profit contribution multiplied by expected customer lifetime, and CAC is monthly sales and marketing spend divided by new customers acquired.
How do you calculate customer lifetime from churn?
A simple shortcut is customer lifetime = 1 divided by churn rate as a decimal. For example, 4% monthly churn gives an estimated lifetime of 25 months.
Why is gross margin included in the formula?
Gross margin adjusts revenue into gross profit contribution. This gives a more realistic estimate of value than using top-line revenue alone.
How do you calculate CAC from funnel data?
First estimate new customers from leads multiplied by conversion rate, then divide monthly sales and marketing spend by those new customers.
Can the ratio be too high to trust?
Yes. Extremely high ratios can happen when churn is entered too low, spend is understated, or conversions are attributed to the wrong period.
Is this formula best for SaaS and recurring revenue businesses?
Yes. It is most useful when customers generate ongoing monthly revenue or repeat purchases over time.
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