CAC Payback Formula
The CAC Payback Formula helps you determine how many months it takes for the gross profit generated by a new customer to cover their initial acquisition cost, a vital metric for cash flow and marketing efficiency.
Bottom Line
The CAC Payback Formula helps you determine how many months it takes for the gross profit generated by a new customer to cover their initial acquisition cost, a vital metric for cash flow and marketing efficiency.
CAC Calculator
Calculate customer acquisition cost, payback period, and LTV:CAC efficiency.
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Formula
Copy the exact expression or work through it step by step below.
CAC Payback Months = Customer Acquisition Cost / Monthly Gross Margin Per Customer Variables
CPM
CAC Payback Months
The number of months of gross margin needed to recover the cost of acquiring a customer. Lower is better; under 12 months is a common SaaS target.
CAC
Customer Acquisition Cost
The fully loaded cost to acquire one customer, in currency units. The amount that must be paid back. See the CAC formula for how it is built.
MGMC
Monthly Gross Margin Per Customer
The gross margin one customer generates per month, in currency units (monthly revenue times gross-margin percent). The monthly amount that chips away at CAC.
Step By Step
- 1
Set the baseline case with the real calculator inputs.
Sales + Marketing Spend = $32,000, New Customers = 40, Monthly ARPU = $129, Gross Margin Percent = 78.0%
- 2
The tool derives CAC from spend divided by new customers, then builds the denominator from monthly revenue per customer times the gross-margin percent.
ARPU 129 at a 78% gross margin yields about 100.6 of monthly gross margin per customer.
- 3
Apply the formula and read the first calculator outputs, not just the headline assumption.
The calculator lands with customer acquisition cost at $800, monthly gross profit at $100.62, and payback at 7.95 months.
- 4
Re-run with a lower gross-margin assumption to see how thin margins stretch the payback period and threaten cash runway.
Dropping gross margin from 78% to 60% lengthens payback from 7.95 to about 10.3 months.
Worked Example
CAC Payback sample case
Sales + Marketing Spend
$32,000
New Customers
40
Monthly ARPU
$129
Gross Margin Percent
78.0%
CAC = $32,000 / 40 = $800. Monthly gross margin per customer = $129 times 78% = $100.62. CAC Payback = $800 / $100.62 = 7.95 months.
The calculator lands with customer acquisition cost at $800 and payback at 7.95 months.
Common Variations
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Sources & References
- CAC Payback Period: The Most Important SaaS Metric You Aren't Tracking — Baremetrics
- The Ultimate Guide to CAC Payback Period — ProfitWell
Related Content
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CAC Payback Examples
CAC payback examples across SaaS, e-commerce, and B2B: how long it takes to recoup acquisition cost at different gross margins and average order values.
How to Use a CAC Calculator
Use the CAC calculator: divide loaded sales and marketing spend by new customers, then check LTV:CAC and payback to decide whether to scale acquisition.
What Is CAC? Simply Explained
Calculate Customer Acquisition Cost (CAC) for your SaaS. Learn its formula, real-world impact, and how to optimize it for sustainable growth and profitability.