SaaS Metrics Calculator: Rule of 40, Magic Number, NRR and CAC Payback
Preparing a Seed or Series A raise? Type in your numbers and see the four ratios most investors will check. Each result shows its formula in plain words and the public source behind any benchmark. Everything runs in your browser.
Formula: revenue growth % plus FCF margin %.
Formula: (start + expansion − contraction − churn) divided by start.
Formula: (start − contraction − churn) divided by start.
Formula: (last quarter revenue − prior quarter revenue) × 4, divided by prior quarter sales and marketing spend.
Formula: sales and marketing spend divided by (new MRR × gross margin). The answer is in months.
Data table: every metric, its inputs and formula Click a column to sort
Where the benchmarks come from
A status chip appears only when a public source gives a threshold. Every source below was opened and read on 2026-10-18. These are rules of thumb, not pass or fail tests. They change with company stage, price point and sales model. Gross revenue retention and CAC per new customer show no chip because no public benchmark was used.
- Rule of 40. Corporate Finance Institute, "The SaaS Rule of 40 Explained", published 2024-10-22. Used: a score of 40 or higher is a well performing SaaS company; EBITDA margin is the most common margin, some use free cash flow. Accessed 2026-10-18. corporatefinanceinstitute.com/resources/valuation/rule-of-40
- Net revenue retention. SaaS Capital, "2025 SaaS Retention Benchmarks for Private B2B Companies", published 2025-09-18. Used: for companies with contract values of $25,000 to $50,000, the median is 102%, the top quartile is 111% and the lowest quartile is 97%. Chips use those three numbers, so they fit that price band best. Accessed 2026-10-18. saas-capital.com/research/saas-retention-benchmarks-for-private-b2b-companies
- SaaS magic number. ChartMogul, "SaaS Magic Number". Used: above 0.75 reads as efficient, 0.5 to 0.75 as acceptable, below 0.5 as a reason to improve efficiency first. ChartMogul calls these directional heuristics. Accessed 2026-10-18. chartmogul.com/saas-metrics/magic-number
- CAC payback. Wall Street Prep, "CAC Payback Period", updated 2024-09-17. Used: payback is sales and marketing divided by new MRR times gross margin, and most viable SaaS startups pay back in fewer than 12 months. Accessed 2026-10-18. wallstreetprep.com/knowledge/cac-payback-period
- CAC payback, second source. Corporate Finance Institute, "CAC Payback Period", published 2024-05-06. Used: a strong target is generally less than 12 months. Accessed 2026-10-18. corporatefinanceinstitute.com/resources/saas/cac-payback-period
Questions founders ask
What is the Rule of 40?
The Rule of 40 adds your revenue growth rate to a profit margin. A score of 40 or higher is read as a healthy balance between growth and profit. Corporate Finance Institute notes that EBITDA margin is the most common choice and that some people use free cash flow margin. Pick one, label it, and use the same one every time you report it.
What is the difference between net and gross revenue retention?
Net revenue retention starts with the recurring revenue a group of customers paid a year ago, adds expansion, then subtracts contraction and churn. Gross revenue retention leaves expansion out, so it can never be above 100%. Net shows whether existing customers grow. Gross shows how much revenue you keep before any upsell.
How do you calculate the SaaS magic number?
Take this quarter's revenue minus last quarter's revenue, multiply by 4, and divide by last quarter's sales and marketing spend. ChartMogul describes above 0.75 as a common sign that spend is converting well, and below 0.5 as a sign to fix efficiency first. It calls these directional rules, not hard limits.
How is CAC payback calculated, and what is a good number?
Divide sales and marketing spend by the new monthly recurring revenue you added times your gross margin. The result is the number of months it takes to earn the spend back. Wall Street Prep and Corporate Finance Institute both describe under 12 months as a healthy target. The right number depends on your price point and sales model.
Do these numbers decide whether I can raise money?
No. They are inputs to a conversation, not a pass or fail test. Stage, price point, sales model and the story behind the numbers all matter. This calculator runs in your browser and does not send your inputs anywhere.