Expansion CAC Ratio
Fully-loaded S&M plus Customer Success expense attributable to expansion divided by expansion CARR generated in the period. Per SMSB, the efficiency read on the upsell / cross-sell / land-and-expand motion. Distinct from the new-logo CAC ratio because the cost base often includes CSMs whose primary metric is retention but whose secondary metric is expansion — boards expect to see that allocation called out. Common pitfall: excluding CS comp entirely understates the true cost of expansion; including all of CS overstates it. The SMSB standard prescribes a documented allocation rule (typically tied to expansion-quota OTE share). — Sales KPI anchored to SaaS Metrics Standards Board.
Rogue ID: sales.expansion_cac_ratio
Type: Number
Domain: Sales
Definition
Fully-loaded S&M plus Customer Success expense attributable to expansion divided by expansion CARR generated in the period. Per SMSB, the efficiency read on the upsell / cross-sell / land-and-expand motion. Distinct from the new-logo CAC ratio because the cost base often includes CSMs whose primary metric is retention but whose secondary metric is expansion — boards expect to see that allocation called out. Common pitfall: excluding CS comp entirely understates the true cost of expansion; including all of CS overstates it. The SMSB standard prescribes a documented allocation rule (typically tied to expansion-quota OTE share).
Formula
Expansion CAC Ratio = (S&M + CS spend allocated to expansion in period) / (Expansion CARR generated in period). Per SMSB §Expansion CAC Ratio: allocation rule for cross-functional comp (typically split by quota share of OTE) must be documented and consistent.Why it matters
Validates the financial logic of "expansion is cheaper than acquisition" — when this is healthy, the company should bias growth investment toward post-sale; when it inverts (Expansion CAC ≥ New CAC), the expansion motion is broken and acquisition is the only available lever.
How to interpret
Per SMSB convention, healthy Expansion CAC Ratio is typically 3–5× cheaper than New CAC Ratio — i.e. 0.2–0.5 when New CAC Ratio is ~1.5. Expansion CAC Ratio > 1.0 is a yellow flag (expansion costs as much as it earns); inversion vs New CAC Ratio is a red flag warranting a CS / sales-team org review.
Calculation policy
How an AI agent should compute this KPI from messy company data. Free-text rules consumed at reasoning time — not a deterministic DSL. The most common ways to get this wrong are listed under Common miscomputations.
Inclusion rules
- Numerator: S&M + Customer Success spend allocated to the expansion motion (upsell / cross-sell / land-and-expand).
- Denominator: expansion CARR generated in the period.
- CS comp is partly in scope: include the share of CSM cost attributable to expansion (typically the fraction of OTE tied to an expansion quota), per a documented rule.
Exclusion rules
- New-logo S&M spend from the numerator (goes in
sales.new_cac_ratio). - The retention-only share of CS comp — CSMs whose comp is purely tied to renewal/retention, not expansion.
- New-customer CARR and renewal CARR from the denominator.
Required inputs
- S&M + CS spend allocated to expansion.
- Expansion CARR for the period.
- The documented allocation rule for cross-functional (CS) comp.
Data-source priority
- Financials + documented CS/S&M allocation model.
- CRM for expansion CARR.
Edge cases
- CS team with no expansion quota at all: expansion is AE-driven; CS comp share is ~0 and the numerator is AE-expansion-comp only.
- Product-led expansion (self-serve upgrades, no human touch): the numerator may be near-zero — Expansion CAC Ratio approaches zero, which is correct and worth calling out as a strength.
- Allocation-rule change: re-state prior periods.
Validation checks
- Expansion CAC Ratio should be materially lower than New CAC Ratio — healthy SaaS expansion is typically 3–5× cheaper per dollar (≈ 0.2–0.5 when New CAC Ratio ≈ 1.5).
- Expansion CAC Ratio ≥ New CAC Ratio is a red flag — the expansion motion is broken; investigate before reporting it as a number without commentary.
- Blended CAC Ratio must sit between New and Expansion CAC Ratio.
Common miscomputations
- Excluding CS comp entirely — understates the true cost of expansion, makes the motion look free.
- Including ALL of CS comp — overstates it; most CS comp is retention, not expansion. Use the documented allocation.
- Using ARR instead of CARR in the denominator.
- Reporting Expansion CAC Ratio in isolation — it is only meaningful next to New CAC Ratio (the comparison IS the insight).
Related KPIs
sales.blended_cac_ratiosales.new_cac_ratiosales.expansioncustomers.net_revenue_retentionsales.carr
Source
SaaS Metrics Standards Board · section: Expansion CAC Ratio — published 2023-01-01.
Why does this cite SaaS Metrics Standards Board? Read the ontology methodology for the published vs editorial tier system, attribution rules, and dispute process.
Metric definitions reference standards published by the SaaS Metrics Standards Board (saasmetricsboard.com). imboard is not affiliated with, endorsed by, or a member of SMSB.
Stage relevance
| Company stage | Priority |
|---|---|
| Series A | Recommended |
| Series B | Recommended |
| Series C+ | Recommended |
| Public | Recommended |
Suggested for stages: Series A, Series B, Series C+, Public.
Default owning functions
- Sales
- Finance
Machine-readable
- This KPI as JSON:
/api/ontology/sales/expansion_cac_ratio.json - All Sales KPIs:
/api/ontology/sales.json - Full catalog:
/api/ontology/index.json
CARR
Contracted Annual Recurring Revenue — recognized MRR × 12 plus the annualized value of contracts that are signed but not yet live (i.e. implementation, ramp, deferred-start). Per the SMSB standard, CARR sits between ARR (live only) and pipeline (unsigned) on the revenue-certainty spectrum: contractually committed but not yet delivered. Boards reading CARR > ARR gap can quantify the in-flight implementation backlog and the leading indicator of next-period ARR. Common pitfall: counting verbal commitments or LOIs as CARR — only signed contracts qualify under the SMSB definition. — Sales KPI anchored to SaaS Metrics Standards Board.
Gross Margin
Recognized revenue minus cost of goods sold (COGS), divided by recognized revenue, expressed as a percentage. The single best read on whether the business model can ever generate operating leverage — a low gross margin caps every downstream efficiency metric (CAC payback, LTV/CAC, Rule of 40). For SaaS, COGS includes hosting, third-party software, customer support, and customer-success cost-of-service. Common pitfall: omitting customer success from COGS inflates the margin and breaks comparability with peer benchmarks. Anchored to KBCM/Sapphire SaaS Survey 2024 §Gross Margin. — Sales KPI anchored to KBCM/Sapphire SaaS Survey 2024 (15th Annual).