As developers, we love shipping features, optimizing database queries, and exploring new frameworks. But when it comes to the business side of things—calculating MRR, LTV, and CAC—we often resort to disorganized Excel sheets or completely ignore the numbers until it's too late.
If you are an indie hacker or building a SaaS product, you can't afford to ignore unit economics. Your code might be perfectly clean, but if your CAC (Customer Acquisition Cost) is higher than your LTV (Lifetime Value), your SaaS will eventually run out of cash.
Here is a quick, developer-friendly crash course on the 3 core SaaS metrics you must track, and a free toolkit to automate the math.
- MRR (Monthly Recurring Revenue) MRR is the baseline of your SaaS. It is the predictable revenue you expect to receive every month.
The Developer's View:
Think of MRR as your cron job for revenue. It fires predictably every 30 days. But it gets complicated when you factor in upgrades, downgrades, and churns.
The Formula:
Net New MRR = New MRR + Expansion MRR - Contraction MRR - Churned MRR
Tip: Don't hardcode one-time setup fees into your MRR calculations. MRR should strictly be subscription-based revenue.
- LTV (Customer Lifetime Value) LTV tells you how much revenue a single user will generate off your product before they eventually cancel (churn).
The Formula:
LTV = ARPU (Average Revenue Per User) / Customer Churn Rate
If your average user pays $20/month, and your churn rate is 5% (0.05), your LTV is $400. That means you can safely spend up to a certain amount to acquire a customer and still be profitable.
- CAC (Customer Acquisition Cost) How much money did you spend on marketing, ads, and sales to acquire one new paying user?
The Formula:
CAC = Total Sales & Marketing Expenses / Number of New Customers Acquired
The Golden Ratio (LTV:CAC):
A healthy SaaS business aims for an LTV:CAC ratio of at least 3:1. If your LTV is $400, you shouldn't spend more than $133 to acquire a user.
Stop Building Your Own Spreadsheets (Use This Instead)
As a builder, your first instinct might be to code your own internal dashboard to track these metrics or build complex Excel macros. Don't do it. It's a trap that distracts you from building your actual product.
Instead of reinventing the wheel, I built SaaS Metrics Box.
It is a completely free, lightweight suite of calculators designed specifically for SaaS founders and indie hackers.
Zero friction: No sign-ups, no paywalls, no API keys to configure.
Instant results: Plug in your numbers and instantly calculate your MRR trajectory, LTV:CAC ratio, churn dynamics, and ROAS.
Made for bootstrappers: Get the exact math you need to check your business health in 10 seconds.
If you are currently building a SaaS, bookmark SaaS Metrics Box and run a quick sanity check on your unit economics.
Drop a comment below if you have any questions about measuring SaaS metrics. Happy shipping! 🚀
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