Customer Acquisition Cost (CAC) is the total amount spent on sales and marketing in a given period divided by the number of new customers closed in that same period. It is one of the most cited metrics in B2B SaaS, and one of the most frequently miscalculated.
At a glance
- Formula: total sales and marketing spend divided by net new customers closed.
- Used by finance, RevOps, and investors to assess growth efficiency.
- Meaningful only when paired with CLV or CAC Payback Period.
- Common pitfall: excluding salaries and only counting ad spend.
- Should be tracked by channel, not just as a single blended number.
How is CAC actually calculated?
The formula is straightforward. The inputs are where teams get sloppy. Total spend means everything tied to acquiring customers: salaries, commissions, ad spend, tools, agency fees, event costs, and contractor hours connected to demand generation or sales. Divide that by closed-won new logos only, not expansions or renewals. If you spent $200,000 in Q1 and closed 20 new customers, your CAC is $10,000.
The trickier issue is the time-lag problem. A deal that closes in Q1 probably started in Q4. Matching spend and customers to the same calendar period distorts the number. A more accurate approach offsets spend by your average sales cycle length. If your cycle runs 90 days, compare Q4 spend against Q1 new customers.
Why does CAC matter for B2B revenue teams?
CAC by itself tells you almost nothing. Paired with CLV (Customer Lifetime Value), it tells you whether your growth is sustainable. A CAC of $10,000 is fine if that customer generates $80,000 in gross margin over their lifetime. It is a serious problem if they churn in 14 months at $12,000 ARR.
The ratio most investors and operators watch is LTV:CAC. A 3:1 ratio is the common benchmark, but that number shifts depending on gross margin, churn rate, and how capital-efficient the business needs to be. Early-stage companies often run at 2:1 while building pipeline density. Later-stage companies with predictable retention can tolerate higher CAC if payback periods stay under 18 months.
What does CAC reveal about channel mix?
Breaking CAC out by channel turns a single blended number into a decision-making tool. If inbound CAC is $4,000 and outbound CAC is $18,000, that gap is a signal about where to allocate budget and headcount, not just a measure of efficiency.
Comparing CAC across motions also requires normalizing for deal size. An ABM program may show higher CAC per account in the short term but lower CAC per dollar of ARR when average contract value is significantly larger. Looking at CAC as a percentage of ACV gives a more useful comparison than the raw number alone.
Common CAC mistakes and misconceptions
- Excluding salaries. Counting only ad spend and ignoring fully loaded SDR and AE headcount produces a number that looks good but means nothing.
- Blending new and expansion revenue. Upsells and cross-sells carry a different cost profile. Mixing them with new logo CAC obscures both figures.
- Ignoring CAC Payback Period. A $15,000 CAC with a 9-month payback can be a stronger business than a $6,000 CAC with an 18-month payback, depending on burn rate.
- Treating CAC as a fixed number. CAC shifts with go-to-market motion, market saturation, and team productivity. Reviewing it quarterly matters more than perfecting the calculation once.
How does CAC connect to adjacent metrics?
CAC Payback Period tells you how many months of gross margin it takes to recover acquisition cost. That is the number that determines whether a business can grow without raising additional capital.
Churn Rate directly affects whether the CLV:CAC ratio holds over time. A company running at 2% monthly churn is effectively resetting its CAC problem every few months, regardless of how efficiently it acquires customers in the first place.