About the SaaS Metrics Calculator
Subscription businesses live and die by a handful of numbers. This calculator takes one month of data, the customers you started with, won and lost and the recurring revenue added, upgraded, downgraded and cancelled, plus your sales and marketing spend and gross margin. It returns your ending MRR and ARR, customer churn, gross revenue churn, net revenue retention, average revenue per customer, customer acquisition cost, lifetime value, the LTV to CAC ratio and the CAC payback in months. Use it for a quick health check before a board update or an investor chat. The numbers never leave your browser.
Updated October 2026
How to use the SaaS Metrics Calculator
- 1Enter the customers you had at the start of the month, the new ones and the ones you lost.
- 2Enter the MRR at the start and the movements: new, expansion, contraction and churned.
- 3Add your sales and marketing spend for the month.
- 4Enter your gross margin as a percentage.
- 5Read the ratios and compare them with the rules of thumb in the guide below.
The numbers that matter
Revenue growth tells you how fast you are moving, but churn and retention tell you whether the growth will last. A business that adds 5 percent a month and loses 4 percent has little to show for its effort. Look at customer churn and net revenue retention together: if expansion revenue covers cancellations, you can grow even without new customers.
Unit economics tie it together. If winning a customer costs more than the gross profit they bring over their life, each sale makes you poorer. LTV to CAC and the payback period are the two quick tests for that.
Rules of thumb, not laws
- Monthly customer churn: under 2 percent is strong for small business products; 5 percent is a warning sign.
- Net revenue retention: above 100 percent is good, above 120 percent is excellent.
- LTV to CAC: aim for 3 or more.
- CAC payback: under 12 months for self-serve, up to 18 for sales-led products.
- Gross margin: 70 to 80 percent or more is typical for software.
Going further
Use the Break-Even Calculator to find how many customers cover your costs, the Profit Margin Calculator to check your margin and the Percentage Change Calculator to compare this month with last month. The Pro Rata Calculator helps work out partial months for upgrades and mid-month starts. These figures are estimates from the data you type and should be checked against your accounting.
Features
- MRR, ARR and month growth
- Customer churn and gross revenue churn
- Net revenue retention
- CAC, LTV and the LTV to CAC ratio
- CAC payback in months
- Sensible error checks
- Private, nothing uploaded
Frequently asked questions
What is MRR?
Monthly recurring revenue is the predictable subscription revenue you expect each month. Yearly plans are counted as one twelfth of their price.
How is churn calculated here?
Customer churn is the customers lost divided by the customers at the start of the month. Gross revenue churn is churned plus contraction MRR divided by starting MRR.
What is net revenue retention?
It is the revenue you keep from the customers you had at the start, after upgrades, downgrades and cancellations, divided by the starting revenue. Above 100 percent means existing customers grow on their own.
How is LTV worked out?
It is the average revenue per customer multiplied by gross margin and divided by monthly customer churn. It assumes churn stays constant, which makes it a rough guide.
What is a good LTV to CAC ratio?
Many teams aim for 3 to 1 or better. Under 1 means you lose money on each customer over their lifetime, and a very high ratio can mean you are underinvesting in growth.
What is CAC payback?
It is the number of months of gross profit from a new customer needed to repay the cost of winning them. Under 12 months is often considered healthy for small business software.
Which spend should I count?
Include sales and marketing salaries, ads, tools and commissions for the month in which they were spent, to get a fully loaded cost per new customer.