How to Calculate Customer Acquisition Cost | CAC
- Sum all sales and marketing costs divided by customers acquired in period
- Include fully loaded costs: people, tools, content, ads, commissions
- Segment by channel to identify which acquisition sources are efficient
How to Calculate Customer Acquisition Cost
The e-commerce company spent $180,000 on Facebook ads and acquired 2,400 customers. The founder said his CAC was $75.
I asked about the marketing team's salaries, the agency retainer, the attribution software, and the free shipping offers. We recalculated: true CAC was $142.
He'd been celebrating profitable unit economics that didn't exist. Every new customer lost money.
Customer acquisition cost determines whether you can afford to grow. Get the number wrong and you'll spend yourself into bankruptcy.
CAC = Total Sales and Marketing Costs / Number of New Customers Acquired
Sounds simple. The complexity hides in "total costs."
Include:
• Paid advertising (all channels)
• Marketing team salaries and benefits
• Sales team salaries and commissions
• Marketing software and tools
True CAC: $142
Monthly vs. Blended CAC
Monthly CAC shows current performance: this month's spend divided by this month's new customers.
The problem: marketing spend and customer acquisition don't align perfectly. Ads running in March might convert customers in April. Content published in January might drive sales in June.
Blended CAC (12-month rolling average) smooths these timing differences. More acselect but less responsive to recent changes.
Use both:
• Monthly CAC for tactical decisions (is this campaign working?)
CAC by Channel
Aggregate CAC hides channel performance. You need CAC for each acquisition source.
Referrals: $24,000 cost (program incentives), 400 customers = $60 CAC
Google and referral customers cost half what Facebook customers cost. This changes budget allocation decisions.
ACTION: Break out your costs and customer counts by channel. Calculate channel-specific CAC.
Payback Period = CAC / Monthly Gross Profit per Customer
A customer with $142 CAC and $23 monthly gross profit takes 6.2 months to pay back.
Target payback periods:
• SaaS businesses: 12-18 months
• E-commerce: 3-6 months (shorter due to lower retention)
• Subscription services: 6-12 months
• Professional services: 1-3 months (higher project values)
Payback exceeding these ranges signals problems - either CAC is too high or margins are too thin.
ACTION: Calculate your CAC payback period. Compare against industry targets.
Customer Heartbeat and Acquisition
Your Customer Heartbeat vital sign tracks retention and loyalty metrics. It directly connects to CAC evaluation.
High Customer Heartbeat (strong retention): Higher CAC is acceptable because customers stay longer and generate more lifetime value.
Low Customer Heartbeat (poor retention): Even low CAC becomes problematic if customers leave quickly.
A business with 85% annual retention can afford higher CAC than one with 60% retention, even if monthly revenue per customer is identical.
ACTION: Compare your CAC against your Customer Heartbeat metrics. Are you acquiring customers who stick?
CAC to LTV Ratio
The relationship between acquisition cost and lifetime value determines viability.
Target ratios:
• Below 1:1 = Losing money on every customer
• 1:1 to 2:1 = Barely viable, no room for error
• 3:1 = Healthy baseline target
• 4:1 to 5:1 = Strong economics, room for investment
• Above 5:1 = May be underinvesting in growth
Average LTV: $340
CAC: $142
LTV:CAC = 2.4:1
At 2.4:1, they're marginally viable - not losing money but not building a moat. Reducing CAC to $100 would push the ratio to 3.4:1.
ACTION: Calculate your LTV:CAC ratio. Is it above 3:1?
Four paths to lower CAC:
Improve conversion rates. Same spend, more customers. A/B test landing pages, simplify checkout, reduce friction.
Shift to lower-cost channels. Move budget from $138 CAC channels to $60 CAC channels. Test new channels continuously.
Increase organic acquisition. Content marketing, SEO, and word-of-mouth have high upfront costs but declining CAC over time.
Improve targeting. Better audience definition reduces wasted spend. Narrower campaigns often convert better.
The e-commerce company shifted 30% of Facebook budget to referral programs and Google. Combined CAC dropped from $142 to $118.
ACTION: Identify your highest-CAC channel. Develop a plan to reduce its cost or shift budget elsewhere.
Put this into practice
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