If you’re running a SaaS startup, not all metrics are created equal. Investors, board members and even your own team will throw around acronyms like MRR, CAC, LTV and NRR – but which ones actually matter as you scale? More importantly, which ones help you make better decisions?
If you’re at the growth stage – traction, paying customers and a push towards scale – here are the seven metrics that should be driving your focus.
As with all our articles, please don’t take this as personal tax, financial or other advice (you need to speak to us for that).
If you’d like help building investor-ready financials around these metrics, take a look at our financial modelling service.
1. Monthly Recurring Revenue (MRR) and Annual Recurring Revenue (ARR)
If you’re a SaaS business, recurring revenue is the foundation of everything. Unlike one-off sales models, your valuation, investor interest and ability to scale all depend on predictable, compounding revenue.
Why it matters:
- Tracks revenue growth trends over time.
- Shows investors the predictability and stability of your business.
- Helps with cash flow forecasting and hiring decisions.
How to calculate it: MRR = Total subscription revenue per month. ARR = MRR × 12.
Watch out for false MRR growth – if revenue is increasing due to large one-off discounts or annual deals counted in full upfront, it may not reflect the underlying health of the business.
2. Net Revenue Retention (NRR) – The Investor Favourite
Net Revenue Retention measures how well you’re retaining and expanding revenue from your existing customer base. It’s one of the metrics UK investors pay closest attention to, because it tells them whether your business can grow even if new customer acquisition slows down.
Why it matters:
- If NRR is over 100%, you’re growing revenue without needing new customers.
- A high NRR signals strong expansion revenue from upsells and cross-sells.
- It’s a reliable predictor of long-term SaaS health.
How to calculate it: (Revenue from existing customers + expansions – churn) ÷ Starting revenue from existing customers.
If your NRR is below 100%, you’re losing more revenue to churn than you’re gaining from existing customers. UK Series A investors typically want to see NRR at 100% or above as a baseline – anything meaningfully higher is a strong differentiator in a fundraising conversation.
3. Customer Acquisition Cost (CAC) – Are You Paying Too Much for Growth?
Customer Acquisition Cost measures how much you spend to acquire each new customer, including marketing, sales and any associated overhead.
Why it matters:
- If CAC is too high, your growth model isn’t sustainable.
- Helps you decide when and where to invest in marketing and sales.
- Ties directly into LTV to assess overall profitability.
How to calculate it: (Total sales and marketing spend) ÷ (Number of new customers acquired).
If CAC is rising without a corresponding increase in LTV, you’re burning cash inefficiently. That’s the time to reassess your acquisition strategy before it compounds into a larger problem.
4. Lifetime Value (LTV) – The Real Measure of SaaS Success
LTV tells you how much revenue you can expect from a customer over their entire relationship with your business. If your LTV is high, your business has strong customer stickiness and long-term value.
Why it matters:
- Shows the true worth of your customer base.
- Helps you understand how much you can afford to spend on acquisition.
- Investors use high LTV as a signal of strong retention and a scalable model.
How to calculate it: (Average revenue per user (ARPU) × Gross margin) ÷ Churn rate.
Keep your LTV:CAC ratio at 3:1 or higher – meaning you’re earning at least three times more from customers than it costs to acquire them. This is a standard benchmark UK Series A investors use as a quick profitability screen.
5. Churn Rate – The Silent Killer of SaaS Businesses
Churn is the percentage of customers who cancel their subscription in a given period. High churn is a warning sign that your product isn’t delivering enough value, or that you’re acquiring the wrong customers in the first place.
Why it matters:
- High churn cancels out new growth and makes scaling significantly harder.
- Even strong acquisition numbers can’t offset a persistent retention problem.
- Investors won’t back a SaaS business with unsustainable churn.
How to calculate it: (Lost customers in a month) ÷ (Total customers at the start of the month).
If churn is over 5-7% monthly, the issue is rarely the metric itself – it’s usually bad onboarding, poor customer support or wrong-fit customers. Fix the root cause, not just the number.
6. Payback Period – How Fast Do You Recover CAC?
The payback period measures how long it takes to recover the cost of acquiring a customer. A shorter payback period means better cash flow and the ability to reinvest into growth faster.
Why it matters:
- A long payback period puts pressure on cash flow.
- A short payback period means you can reinvest faster into growth.
- Bootstrapped companies need a faster return than VC-backed ones can afford to wait for.
How to calculate it: CAC ÷ ARPU.
Aim for a payback period under 12 months. If it’s significantly longer, you’ll be heavily reliant on outside funding to sustain growth – which isn’t a problem while fundraising is going well, but becomes a real risk when it isn’t.
7. Activation Rate – Are New Users Actually Using Your Product?
Most SaaS businesses track sign-ups, but what actually matters is activation – when a new user completes a key action that makes them meaningfully more likely to stay.
Why it matters:
- Low activation means you’re losing potential long-term customers before they see value.
- Helps you identify where onboarding is breaking down.
- Strong activation drives higher retention and lower churn downstream.
How to calculate it: (Users who complete a key action) ÷ (Total sign-ups).
Define your “aha moment” – the single action that most strongly correlates with a user staying on your platform long-term – and build your onboarding to drive that action as quickly as possible.
Focus on What Moves the Business
Vanity metrics – total sign-ups, website traffic, social followers – can look impressive on a pitch deck without telling you anything meaningful about business health. The seven metrics above are the ones that drive real decisions: where to invest, what’s breaking, and whether your unit economics hold up at scale.
If you’re growing a SaaS business and need help making sense of your numbers, we can help. At Standard Ledger, we work with UK startups to build clear, investor-friendly financials that support growth.
