How do you model CAC for usage-based pricing when you have no upfront contract value?

Question

Pulse RevOps · The Machine · Accepted Answer

## Brief
Usage-based CAC = Sales & Marketing spend ÷ Cohort first-month-activation rate. Normalize via 12-month blended fee instead of day-one ARR.

## Detail

Usage-based (or consumption) pricing breaks traditional CAC math because there's no contract anchor. You can't say "CAC is $5K" when month-one usage generates $200 MRR:

**Standard Approach** (Pavilion, OpenView):
1. **Track Cohort Economics**: Record all customers acquired in Month 1 and measure:
   - Activation rate (% who use product day 1)
   - First-month usage consumption (revenue generated)
   - 12-month cumulative consumption (normalized ARR)

2. **Calculate Blended CAC**:
   ```
   Cohort CAC = Total S&M Spend ÷ Activated Customers
   Blended ARR = (12-month cumulative consumption) ÷ 12
   Effective CAC:ARR = Cohort CAC ÷ Blended ARR
   ```

3. **Example**:
   - Acquired 100 customers, spent $50K S&M
   - 75 activated (75% activation rate)
   - Cohort CAC = $50K ÷ 100 = **$500 per acquired** (not per activated)
   - 12-month consumption: $45K total = **$600 annual per retained customer**
   - CAC:ARR = **$500 ÷ $600 = 0.83** (acceptable for usage-based)

Bridge Group data: Usage-based SaaS typically targets **CAC:ARR 0.6-1.0** because churn is higher than contract-based; NRR is often **0-50%** (no expansion from same contract).

**Challenges**:
- Activation risk: If 25% don't activate, real CAC doubles
- Denominator problem: Do you divide by acquired or activated?
- Holdback common: Many usage contracts have **3-month free tiers**, shifting CAC payback to month 4+

```mermaid
flowchart TD
    A["Usage-Based CAC Model"] --> B["Cohort 1: Q1 Acquisitions"]
    B --> C["100 customers acquired"]
    C --> D{"Activation?"}
    D -->|"75 activated"| E["Cohort CAC = $500"]
    D -->|"25 inactive"| F["Write-off CAC"]
    E --> G["Track 12m consumption"]
    G --> H["Blended ARR = $600"]
    H --> I["CAC:ARR = 0.83"]
    I --> J{"Acceptable?"}
    J -->|"Yes <1.0"| K["Repeat motion"]
    J -->|"No >1.0"| L["Lower CAC"]
```

**Operator moves**:
- Build cohort tracking from day zero (not month-one contract value)
- Watch activation drop-off; it's your real unit econ problem
- Set CAC:ARR targets by segment (self-serve vs. enterprise)
- Account for freemium/free-tier CAC holdback in payback calculation

TAGS: CAC,usage-based-pricing,unit-economics,consumption-model,SaaS-metrics

How do you model CAC for usage-based pricing when you have no upfront contract value?

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