Company-level CAC payback

Unit economics define payback on a per-customer basis. Boards also look at a company-level CAC payback in months: how long until the gross profit from newly acquired recurring revenue pays back what we spent to get it?

Walking through the formula

CAC payback (months) ≈
  (S&M in period) / (net new ARR in period × gross margin) × 12

Variants abound (some use new ARR only; some use contribution margin). Pick one and keep it.

Benchmarks people still quote: under 12 months excellent for SMB/PLG; 12–18 months fine for mid-market; 18–24 months common in enterprise with high NRR (you get paid back via expansion). Past ~24–36 months you are underwriting a lot of retention and fundraising risk.

Worked sketch: S&M $3M in a year, net new ARR $4M, gross margin 80%:

Annual gross profit from new ARR ≈ 4.0 × 0.80 = $3.2M
Payback ≈ 3.0 / 3.2 × 12 ≈ 11.3 months

Inference-heavy products with thinner gross margins lengthen payback for the same S&M and ARR. Dropping from 80% to 55% stretches payback by 0.80 / 0.55 ≈ 1.45×. Same sales machine, slower cash recovery, because more of each ARR dollar is COGS.

Usage-based ARR also wiggles quarter to quarter. Define net new ARR carefully (committed vs pure consumption) or the ratio becomes noise.

Common mistakes

• Leaving gross margin out. Payback on revenue, not gross profit, is too optimistic — especially for AI.
• Mixing new ARR and net new ARR without saying which. Expansion vs logos changes the story.
• Underwriting 36-month payback without the NRR to finish the job.

Check yourself

S&M $3M, net new ARR $4M, gross margin 80%. Payback in months?

About 11.3. 3.0 / (4.0 × 0.80) × 12 ≈ 11.3.

Gross margin falls from 80% to 55%. What happens to payback?

It stretches by about 1.45×. Same S&M and ARR, slower recovery.

Key takeaways

• Company CAC payback folds S&M, net new ARR and gross margin into months-to-recover.
• Under 12 months is excellent for SMB/PLG; 18–24 is common in enterprise with high NRR.
• AI COGS lengthen payback. The margin is in the denominator.
• Say whether you use new ARR or net new ARR, and keep the definition.

Further learning

Next, Rule of 40.