CAC Payback & Sales Efficiency Calculator
A manual worksheet for calculating your CAC payback period, LTV:CAC, and Magic Number from your own inputs, benchmarked against SaaS efficiency norms by performance tier.
How to use it
Plug your own S&M spend, new customers, ACV, and gross margin into the formulas, compare your result to the benchmark table, then follow the diagnostic guide for whichever metric is weak.
What's inside
- Input worksheet (S&M spend, new customers, ACV, gross margin, lifetime)
- CAC, CAC Payback, LTV, LTV:CAC, and Magic Number formulas
- Fully worked numeric example
- Benchmark table by performance tier
- Diagnostic guide for a bad payback, LTV:CAC, or Magic Number
A worksheet, not a black box, every formula is shown so you can run this by hand or drop straight into a spreadsheet.
Step 1: Gather your inputs
| Input | Your number |
|---|---|
| Total Sales & Marketing spend, last quarter (fully loaded: salaries, commissions, tools, ad spend, events) | $______ |
| New customers acquired, same quarter | ______ |
| Average Annual Contract Value (ACV) of new customers | $______ |
| Gross margin % (revenue minus COGS/hosting/support costs, as a %) | ______% |
| Average customer lifetime (years), or use 1 ÷ annual churn rate | ______ |
Step 2: Core formulas
Customer Acquisition Cost (CAC): CAC = Total S&M Spend ÷ New Customers Acquired
CAC Payback Period (in months): CAC Payback (months) = CAC ÷ (ACV × Gross Margin % ÷ 12)
LTV (simple version): LTV = (ACV × Gross Margin %) × Average Customer Lifetime (years)
LTV:CAC Ratio: LTV:CAC = LTV ÷ CAC
Magic Number (quarterly, sales efficiency of net new S&M spend): Magic Number = (This Quarter's New ARR × 4) ÷ Last Quarter's S&M Spend
Step 3: Worked example
| Input | Example value |
|---|---|
| S&M spend (last quarter) | $500,000 |
| New customers acquired | 40 |
| Average ACV | $30,000 |
| Gross margin | 75% |
| Average customer lifetime | 3 years |
Calculations:
- CAC = $500,000 ÷ 40 = $12,500
- Monthly gross-margin-adjusted revenue per customer = ($30,000 × 0.75) ÷ 12 = $1,875/month
- CAC Payback = $12,500 ÷ $1,875 = 6.7 months
- LTV = ($30,000 × 0.75) × 3 = $67,500
- LTV:CAC = $67,500 ÷ $12,500 = 5.4x
Step 4: Benchmark against your stage
| Metric | Best-in-class | Healthy | Warning zone | Problem |
|---|---|---|---|---|
| CAC Payback (months) | < 12 | 12–18 | 18–24 | > 24 |
| LTV:CAC | > 5x | 3–5x | 2–3x | < 2x |
| Magic Number | > 1.0 | 0.75–1.0 | 0.5–0.75 | < 0.5 |
| Gross margin (SaaS) | > 80% | 70–80% | 60–70% | < 60% |
(Benchmarks skew shorter/tighter for SMB-focused motions with fast sales cycles, and longer for enterprise motions with 12+ month sales cycles and high land-and-expand potential: read your number against your own motion, not against a generic "SaaS average.")
In the worked example above: a 6.7-month payback and 5.4x LTV:CAC land in "best-in-class": this business can responsibly accelerate S&M spend to grow faster, because it's getting its money back fast and each customer is worth well more than it costs to acquire.
Step 5: Diagnose a bad number
If CAC Payback is too long (>18-24 months), check in this order:
- Is ACV genuinely too low for the cost of sale? → Consider raising price/packaging, or moving down-market to a lower-touch/PLG motion.
- Is sales cycle inflating cost per deal (reps carrying deals too long)? → This is often a sales execution/qualification problem, not a pricing problem, check win rate by stage and time-in-stage.
- Is S&M spend inflated by inefficient channels (high-cost ads, oversized SDR team for the pipeline it generates)? → Audit spend by channel against pipeline sourced, not just total spend.
If LTV:CAC is too low (<3x), check in this order:
- Is churn the real problem (short average lifetime), which no amount of cheaper acquisition fixes? → Look at retention/expansion before touching CAC.
- Is gross margin compressed by expensive implementation/support that should be priced into the deal? → Revisit packaging.
- Is CAC itself just too high relative to deal size? → Revisit the payback diagnosis above.
If Magic Number is low (<0.5), the fastest read: you're spending on S&M faster than it's producing new ARR: before hiring more reps or increasing ad spend, find out whether it's a pipeline-generation problem (not enough qualified leads for the reps you have) or a conversion problem (reps/funnel not converting the pipeline that exists). Adding more spend to a broken conversion funnel makes the Magic Number worse, not better.