Rule of 40 and Net Revenue Retention: The Two SaaS Metrics Investors Actually Check

For SaaS companies, investors want to know more than how fast revenue is growing. They also want to understand whether that growth is efficient, sustainable, and supported by strong customer retention.  

Two metrics that help answer these questions are the Rule of 40 and Net Revenue Retention (NRR). The Rule of 40 measures the balance between growth and profitability, while NRR shows how much recurring revenue a company retains and expands from existing customers.  

Together, these SaaS metrics give investors a clearer view of business quality, revenue durability, and long-term growth potential.

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What Is the Rule of 40 in SaaS ?

The Rule of 40 is a SaaS performance benchmark used to assess whether a company is balancing revenue growth with profitability. It states that a SaaS company’s growth rate plus its profit margin should equal or exceed 40%. 

The metric is useful because SaaS businesses often prioritize growth at different stages. A fast-growing company may operate at a lower margin, while a more mature SaaS company may grow more slowly but generate stronger profits. The Rule of 40 gives investors a simple way to evaluate that trade-off. 

How to Calculate the Rule of 40

The basic Rule of 40 formula is: 

Rule of 40 = Revenue Growth Rate + Profit Margin 

For example, if a SaaS company has: 

• Annual revenue growth of 28% 
• Profit margin of 15% 

Its Rule of 40 score would be: 

28% + 15% = 43% 

Since the combined score is above 40%, the company meets the Rule of 40 benchmarks. 

Companies may use EBITDA margin, operating margin, or free cash flow margin as the profitability component. What matters most is using the same definition consistently when comparing performance across reporting periods. 

What Counts as a Good Rule of 40 Score?

A Rule of 40% or higher is generally considered strong because it indicates that the business is producing a healthy combination of growth and profitability. 

A simple way to interpret the score is: 

• Above 40%: Strong balance of growth and profitability 
• Around 40%: Generally, meets the benchmark 
• Below 40%: May indicate slower growth, weak margins, or both 

However, the score should not be viewed in isolation. Investors may also consider the company’s stage, recurring revenue growth, cash generation, customer retention, and overall unit economics before judging performance. 

Growth Rate vs. Profitability: How the Trade-Off Works

The Rule of 40 does not require a SaaS company to have both high growth and high profitability. Instead, one can partially offset the other. 

A rapidly expanding SaaS company, for instance, might grow revenue by 55% while operating at a -10% margin. Its Rule of 40 score would still be 45%. 

By contrast, a mature SaaS company might grow by only 15% but generate a 30% profit margin, also resulting in a score of 45%. 

This is why the metric is useful for investors. It provides a common framework for comparing SaaS businesses with different growth strategies and levels of maturity. 

Simple Rule of 40 Example

Consider two SaaS companies:

Company A is growing much faster, but its negative margin brings its Rule of 40 score below the benchmark. 

Company B is growing more slowly, but its stronger profitability produces a Rule of 40 score of 44%. 

For investors, this comparison shows why revenue growth alone is not enough. The Rule of 40 helps reveal how efficiently that growth is being produced and whether the company’s financial model can support it over time. 

What Is Net Revenue Retention?

Net Revenue Retention (NRR) is a SaaS metric that measures how much recurring revenue a company keeps from its existing customers over a specific period after accounting for upgrades, expansions, downgrades, and cancellations. 

Unlike new customer revenue, NRR focuses only on customers the business already had at the beginning of the period. This makes it useful for understanding whether the existing customer base is becoming more or less valuable over time. 

An NRR above 100% means expansion revenue from existing customers is more than offsetting revenue lost through churn and downgrades. 

How to Calculate Net Revenue Retention

The standard NRR formula is: 

NRR = (Starting Recurring Revenue + Expansion Revenue − Contraction Revenue − Churned Revenue) ÷ Starting Recurring Revenue × 100 

For example, suppose a SaaS company begins the year with $1 million in Annual Recurring Revenue (ARR) from existing customers. During the year, it generates: 

• $150,000 in expansion revenue 
• $40,000 in downgrades 
• $60,000 in churned revenue 

Its NRR would be: 

($1,000,000 + $150,000 − $40,000 − $60,000) ÷ $1,000,000 × 100 = 105% 

The company therefore retained and expanded its original customer revenue base by 5%. 

What Revenue Is Included in NRR?

NRR typically includes recurring revenue movements from customers who were already active at the start of the measurement period. 

These include: 

• Starting recurring revenue: ARR or MRR from the existing customer base 
• Expansion revenue: Additional recurring revenue from upgrades, additional users, higher usage, or cross-selling 
• Contraction revenue: Revenue lost when customers downgrade plans or reduce usage 
• Churned revenue: Recurring revenue lost when customers cancel completely 

Revenue from newly acquired customers is not included in NRR. This separation allows investors to see how effectively the SaaS company is growing revenue from its existing customer base without relying on new sales.

What Is a Good NRR for a SaaS Company? 

An NRR above 100% is generally a positive sign because it means revenue expansion from existing customers is exceeding revenue lost through churn and contraction. 

As a simple interpretation: 

• Above 120%: Indicates strong customer expansion and retention 
• 100%–120%: Generally, reflects healthy existing-customer revenue performance 
• Below 100%: Existing customer revenue is shrinking overall 

However, an appropriate NRR benchmark can vary based on the SaaS business model, customer segment, pricing structure, and company maturity. Enterprise SaaS businesses, for example, may have different retention patterns than companies serving smaller customers. 

For investors, the direction and consistency of NRR can be just as important as the headline percentage. 

Simple NRR Example

Consider a SaaS business that starts the quarter with $500,000 in recurring revenue from existing customers. 

During the quarter: 

The NRR calculation would be: 

($500,000 + $75,000 − $20,000 − $30,000) ÷ $500,000 × 100 = 105% 

An NRR of 105% means the company increased recurring revenue from its original customer base by 5%, even after accounting for customers who downgraded or left. 

This is why NRR matters to SaaS investors. It shows whether growth is supported by customers continuing to stay, spend, and expand rather than depending entirely on acquiring new customers. 

How Investors Interpret Different Rule of 40 and NRR Combinations

The Rule of 40 and NRR becomes more useful when investors evaluate them together. One measures the balance between growth and profitability, while the other shows whether existing customers are maintaining or increasing their recurring revenue. 

Different combinations can therefore point to very different strengths and risks within a SaaS business. 

High Rule of 40 + High NRR

A high Rule of 40 score combined with strong NRR is generally the most attractive position. 

It suggests that the SaaS company is balancing growth and profitability effectively while also retaining customers and generating additional revenue from its existing base. 

For investors, this combination can indicate: 

• Efficient and sustainable growth 
• Strong customer retention 
• Healthy expansion revenue 
• Effective pricing and upselling 
• Less dependence on acquiring new customers to maintain growth 

For example, a SaaS company with a Rule of 40 score of 48% and NRR of 118% is showing both strong financial performance and growing value from existing customers. 

High Rule of 40 + Low NRR

A SaaS company can meet or exceed the Rule of 40 while still having relatively weak NRR. 

This may happen when strong new customer acquisition, rapid revenue growth, or high profitability compensates for revenue being lost from existing customers. 

Investors may see strong headline performance, but low NRR can raise questions about: 

• Customer churn 
• Product stickiness 
• Customer satisfaction 
• Pricing or downgrade pressure 
• The cost of continually replacing lost revenue 

If NRR remains below 100%, the company may need increasingly strong new sales just to maintain its overall growth rate. Investors are therefore likely to investigate what is driving customer losses before assuming the Rule of 40 performance is sustainable. 

Low Rule of 40 + High NRR

A high NRR with a low Rule of 40 score tells a different story. 

Customers may be staying, upgrading, and expanding their spending, but the overall business may not yet be growing efficiently enough or generating sufficient profitability. 

This can happen because of: 

• High customer acquisition costs 
• Heavy product development spending 
• Rapid hiring 
• Weak operating margins 
• Slowing new customer acquisition 

Investors may still view strong NRR positively because it suggests the product is delivering ongoing value to customers. However, they will want to understand whether management can translate that customer strength into better growth, margins, and cash generation. 

Low Rule of 40 + Low NRR

When both the Rule of 40 and NRR are weak, investors are likely to look more closely at the underlying business model. 

A low Rule of 40 score suggests that growth and profitability are not currently producing a strong combined result. Low NRR indicates that the company is also losing recurring revenue from its existing customer base. 

Together, these metrics can point to problems such as: 

• High customer churn 
• Weak expansion revenue 
• Slowing growth 
• Rising operating costs 
• Poor unit economics 
• Product-market fit or customer-value concerns 

This does not automatically mean the SaaS business lacks potential. However, investors will generally want to see a clear explanation for the weaker performance and evidence that management has a credible plan to improve retention, growth efficiency, and profitability. 

Ultimately, investors are less interested in whether a SaaS company passes a single benchmark in one period. They want to understand the direction of both metrics, what is driving them, and whether the underlying economics are improving over time. 

How SaaS Finance Teams Can Improve Rule of 40 and NRR Visibility

Improving the Rule of 40 or NRR starts with being able to measure the underlying drivers accurately. SaaS finance teams need consistent revenue classification, customer-level data, and reliable monthly reporting to understand why these metrics are moving and where action is required.

Separate Recurring and Non-Recurring Revenue

SaaS companies should clearly distinguish recurring subscription revenue from implementation fees, consulting income, one-time services, and other non-recurring revenue. 

This separation matters because metrics such as ARR, MRR, revenue growth, and NRR depend on an accurate view of recurring revenue. Mixing one-time income with subscription revenue can make growth appear stronger than it actually is and reduce the reliability of investor reporting. 

Finance teams should maintain consistent revenue classifications across the accounting system, billing platform, and management reports. 

Track Churn, Expansion and Contraction Accurately

Knowing that recurring revenue changed is not enough. Finance teams should understand why it changed. 

Customer revenue movements should be categorized into: 

• New customer revenue 
• Expansion or upsell revenue 
• Contraction or downgrade revenue 
• Churned revenue 

This makes NRR easier to calculate and helps management identify whether growth is being driven by existing customers spending more or by continually replacing customers that have left. 

For example, two SaaS businesses may report identical revenue growth, but the one generating more expansion revenue and experiencing less churn may have a much stronger underlying revenue model. 

Monitor SaaS Metrics by Customer Cohort

Company-wide averages can hide important trends. Breaking SaaS metrics down by customer cohort provides a more detailed view of retention and expansion. 

Finance teams can analyze NRR and churn by factors such as: 

• Customer acquisition period 
• Subscription plan 
• Customer size 
• Industry 
• Geography 
• Sales channel 

A business may have an overall NRR above 100%, for example, while newer customer cohorts are retaining significantly less revenue than older ones. Identifying that trend early gives management an opportunity to investigate onboarding, pricing, product adoption, or customer success issues before they materially affect overall performance. 

Build Reliable Monthly SaaS Reporting

Rule of 40 and NRR should not be metrics calculated only before a board meeting or fundraising round. They should form part of a consistent monthly SaaS reporting process. 

A reliable reporting package can bring together: 

ARR and MRR → Revenue Growth → Churn → Expansion → NRR → Gross Margin → Profitability → Rule of 40 

Tracking these metrics regularly helps finance teams spot changes earlier and explain what is driving them. 

It also improves investor confidence because management can support headline metrics with reconciled financial and operational data rather than relying on one-off calculations. 

Connect Operational Metrics with Financial Forecasts

The greatest value comes from connecting SaaS KPIs with forward-looking financial forecasts. 

Changes in churn, NRR, customer acquisition, pricing, or expansion rates should flow into revenue and profitability projections. For example, declining NRR may reduce future ARR forecasts, while improved expansion revenue could increase expected growth without requiring the same level of new customer acquisition. 

Similarly, finance teams can model how different combinations of revenue growth and profitability affect the company’s future Rule of 40 scores. 

Connecting operational performance with budgeting and forecasting allows management to move beyond reporting what happened and understand how today’s SaaS metrics could influence future growth, margins, and cash flow.  

Bring in Virtual CFO Oversight for Metric Interpretation

Tracking Rule of 40 and NRR accurately is one challenge, knowing what to do when they move in the wrong direction is another. A virtual CFO sits above the day-to-day bookkeeping and reporting layer, reviewing these metrics on a recurring basis and connecting them back to decisions like pricing changes, hiring plans, or customer success investment. 

For example, if NRR starts declining across newer customer cohorts while the Rule of 40 still looks healthy, a Virtual CFO can help finance teams trace whether the issue sits in onboarding, product adoption, or pricing, and translate that into a plan the board or investors can act on. This turns monthly SaaS reporting from a set of numbers into a decision-making tool, rather than a retrospective scorecard.  

Strengthen Your SaaS Finance Function with the Right Virtual CFO

Strong SaaS financial reporting depends on more than tracking a few headline metrics. Businesses need accurate recurring revenue data, reliable monthly closes, consistent KPI reporting, and forecasts that connect operational performance with financial outcomes. This is exactly where a virtual CFO can make the difference: bringing structure to the numbers, flagging what Rule of 40 and NRR trends actually mean for the business, and helping leadership plan ahead instead of just reporting the past.  

At Whiz Consulting, our virtual CFO services helps SaaS businesses go beyond bookkeeping, covering revenue reporting, SaaS KPI dashboards, budgeting and forecasting, and investor-ready financial reporting. Our accounting teams help maintain consistent financial data and reporting processes, enabling SaaS leaders to understand performance clearly and present reliable financial information to boards, investors, and other stakeholders.