The One Metric Most Finance Teams Track Wrong
TL;DR
- A company with a $200K per year AE who closes $2M in new ARR has a significantly different individual-rep contribution to CAC depending on whether fully-loaded comp, base only, or nothing is included for sales headcount.
- The correct CAC formula includes all marketing spend, all sales headcount cost fully-loaded, sales tools and systems, and a portion of marketing headcount cost, which can increase a $50K CAC to $80K when properly calculated.
- A customer paying $10K per year on a product with 60 percent gross margin has an LTV of $60K over 10 years, not $100K, highlighting the importance of using gross profit instead of net revenue in LTV calculations.
Every B2B SaaS finance team tracks CAC and LTV. Most of them are tracking both incorrectly, in ways that make the business look more efficient than it is while hiding the actual levers of unit economics.
The misapplication is not about the formulas. It is about the boundaries of the calculation: what goes into each number, which cohort it applies to, and what the resulting ratio actually measures.
The CAC Problem
The most common CAC error in B2B SaaS is excluding the sales team's time from the calculation. A company with a $200K per year AE who closes $2M in new ARR has an individual-rep contribution to CAC that looks very different depending on whether you include fully-loaded comp, base only, or nothing at all for sales headcount.
The correct CAC formula includes: all marketing spend (paid, content, events, tools), all sales headcount cost fully-loaded (base plus commission plus benefits plus equity amortization), sales tools and systems, and a portion of marketing headcount cost attributable to demand generation.
Most teams include the marketing spend line but use a simplified version of sales cost. A $50K CAC calculated with base-only comp might be $80K when properly loaded. That delta matters when you are modeling payback periods for a fundraise or deciding whether to hire a second AE.
The LTV Problem
The LTV error is usually on the gross margin side. Teams use net revenue in the numerator when they should be using gross profit. A customer paying $10K per year on a product with 60 percent gross margin has an LTV of $60K over 10 years, not $100K.
The second LTV error is using company-average churn when cohort-level churn diverges significantly. If your upmarket customers churn at 5 percent annually and your SMB customers churn at 30 percent annually, a blended 15 percent churn rate produces LTV numbers that are wrong for both segments.
The Right Approach
Calculate CAC and LTV by segment, not in aggregate. Segment by: channel (paid vs organic vs outbound), sales motion (PLG vs enterprise vs partner), and customer size (SMB vs mid-market vs enterprise). Each combination has a different CAC, a different LTV, and a different payback period.
Use gross margin LTV, not revenue LTV. Include fully-loaded sales costs in CAC. This is harder to calculate and will make your numbers look worse. It will also make them accurate.
Measure LTV using observed retention data for cohorts that have been customers long enough to produce meaningful signals. Projecting LTV from a 12-month cohort is a guess. Be explicit about that when presenting to the board.
What Changes When You Get This Right
When finance teams segment properly, the usual finding is that one channel or motion is significantly more efficient than the others and has been hidden by the blended average. The aggregate LTV/CAC of 3:1 might consist of a paid search motion at 1.5:1 and an outbound enterprise motion at 6:1. The right resource allocation decision is not visible until you split the numbers.