Understanding SaaS Metrics: A Guide to ARR, MRR, and Revenue Projections

For software-as-a-service (SaaS) and subscription-based companies, evaluating financial health requires a different approach than traditional retail or one-off sales models. Because revenue is recognized over time rather than all at once, business owners and financial operators rely on specific metrics to measure growth, predict cash flow, and assess customer retention.

Two of the most critical metrics in this ecosystem are Annual Recurring Revenue (ARR) and Monthly Recurring Revenue (MRR). Alongside Average Revenue Per User (ARPU) and churn rates, these figures provide a clear picture of a company's current performance and future trajectory.

This guide explains these core financial concepts, how they interact, and how to manually calculate your business's revenue projections.

The Core Metrics Explained

Before looking at growth projections, it is helpful to establish clear definitions for the baseline metrics used in subscription accounting.

Monthly Recurring Revenue (MRR)

MRR is the normalized monthly revenue a business expects to receive from all active subscriptions. It is a predictable measure of cash flow that smooths out the fluctuations of different billing cycles. For example, if a customer pays $1,200 upfront for an annual plan, that payment is not recognized as a single $1,200 spike in the month it was paid. Instead, it is recognized as $100 of MRR over the course of twelve months.

Annual Recurring Revenue (ARR)

ARR is simply the annualized version of MRR. It projects the recurring revenue a business will generate over a 12-month period, assuming no changes in the current customer base (no new sales, no upgrades, and no cancellations). Enterprise businesses with long-term contracts tend to focus heavily on ARR, while consumer-facing apps with monthly billing cycles often prioritize MRR.

Average Revenue Per User (ARPU)

ARPU measures the average amount of revenue generated from a single active customer over a specific period, usually a month. It helps businesses understand the value of their average customer, which is necessary for setting marketing budgets and calculating Customer Acquisition Cost (CAC) limits.

Net Month-over-Month (MoM) Growth

Growth is rarely a straight line. Every month, a business adds new revenue through sales and upgrades, but it also loses revenue through downgrades and cancellations (churn). Net MoM growth is the actual percentage by which the company's revenue pool expands or contracts after accounting for those losses.

How to Calculate Subscriptions Metrics

The relationship between these figures is straightforward and relies on basic arithmetic. Here are the formulas used to establish a baseline.

Converting MRR to ARR

To find your annual run rate based on your current monthly performance, multiply the MRR by twelve:

$$ARR = MRR \times 12$$

Converting ARR to MRR

To break down an annual contract value into a monthly figure, divide the ARR by twelve:

$$MRR = \frac{ARR}{12}$$

Calculating ARPU

To find the average monthly value of a customer, divide your total MRR by your total number of active paying customers:

$$ARPU = \frac{Total MRR}{Total Active Customers}$$

Calculating Net MoM Growth Rate

To find the actual rate at which your business is growing, subtract your revenue churn percentage from your new revenue growth percentage:

$$Net Growth Rate = New Revenue Growth \% - Revenue Churn \%$$

Step-by-Step Manual Pro Forma Projection

A pro forma projection is a financial forecast based on current assumptions. By taking your current MRR and applying consistent growth and churn rates, you can model what your revenue will look like over the next 12 months.

Here is an example of how to calculate this manually.

The Scenario:

  • Starting ARR: $120,000

  • Total Active Customers: 100

  • Expected MoM New Revenue Growth: 5%

  • Expected MoM Revenue Churn: 2%

Step 1: Establish the Baseline Variables

First, convert the starting numbers into workable monthly figures.

  • Find the MRR: $\frac{\$120,000}{12} = \$10,000$ MRR

  • Find the ARPU: $\frac{\$10,000}{100} = \$100$ per month

Step 2: Calculate Month 1 Adjustments

Next, calculate exactly how much money is coming in and going out during the first month.

  • Starting MRR: $10,000

  • New Revenue Added: $\$10,000 \times 0.05 = \$500$

  • Revenue Lost (Churn): $\$10,000 \times 0.02 = \$200$

  • Ending MRR for Month 1: $\$10,000 + \$500 - \$200 = \$10,300$

Step 3: Calculate Month 2 Adjustments

The ending MRR from Month 1 becomes the starting MRR for Month 2. Because of compounding interest, the flat dollar amounts will change even if the percentages remain the same.

  • Starting MRR: $10,300

  • New Revenue Added: $\$10,300 \times 0.05 = \$515$

  • Revenue Lost: $\$10,300 \times 0.02 = \$206$

  • Ending MRR for Month 2: $\$10,300 + \$515 - \$206 = \$10,609$

Step 4: Determine the Forward Annual Run Rate

If you repeat this process for exactly 12 months, you will reach your ending MRR for Month 12. Let's assume that after 12 rounds of compounding, the Month 12 Ending MRR is $14,257.

To find the Forward Annual Run Rate—which answers the question "What will our ARR be a year from now if we maintain this momentum?"—you multiply that final month's MRR by twelve.

$$Forward ARR = \$14,257 \times 12 = \$171,084$$

The Impact of Churn on Compounding Growth

When projecting long-term revenue, many operators focus heavily on top-line sales growth while underestimating the drag caused by churn.

Because SaaS growth compounds, churn acts as a constant downward pressure on your baseline. In the example above, the company brings in 5% new revenue but loses 2%, resulting in a Net MoM Growth Rate of 3%.

If that same company managed to reduce its churn from 2% to 1% (creating a 4% net growth rate), the 12-month outcome changes drastically. A 1% difference in monthly churn over a year can mean tens of thousands of dollars in difference regarding the Forward ARR, simply because the business is retaining a larger principal amount to compound against in subsequent months.

Common Mistakes in Revenue Tracking

Tracking subscriptions correctly requires strict accounting discipline. Here are frequent errors businesses make when calculating ARR and MRR:

  • Including Non-Recurring Fees: One-time setup fees, consulting charges, or hardware sales should never be included in MRR or ARR calculations. These metrics are strictly for expected, recurring subscription revenue. Including one-off sales will artificially inflate your metrics and ruin your future projections.

  • Confusing Cash Flow with Revenue: If a customer pays $1,200 up front for an annual contract, your bank account goes up by $1,200. However, your MRR only increases by $100. MRR is a revenue recognition metric, not a cash receipts metric.

  • Calculating ARPU Annually: While it is possible to calculate annual revenue per user, ARPU is standardly tracked on a monthly basis across the software industry. Doing otherwise can create confusion when comparing your business benchmarks to industry standards.

  • Ignoring Expansion Revenue: When calculating new revenue growth, it is important to factor in expansion revenue—money gained when existing customers upgrade their plans or buy add-ons. Growth isn't just about acquiring new logos; it is also about expanding the value of current accounts.

Frequently Asked Questions

Can I track ARR if my customers pay on a monthly basis?

Yes. You can annualize any recurring revenue stream regardless of the billing cycle. If you have 500 customers paying $10 a month, your MRR is $5,000 and your ARR is $60,000. It simply projects what your annual revenue would be if all current monthly subscribers stayed for a full year.

What is a healthy Net MoM Growth Rate?

Acceptable growth rates vary wildly depending on the maturity of the company. An early-stage startup might see 10% to 15% net monthly growth, while a mature, publicly traded SaaS company might be very healthy at 1% to 2% net monthly growth.

Should I use customer churn or revenue churn in pro forma models?

For financial modeling, you must use revenue churn. Customer churn measures the percentage of people who left, while revenue churn measures the dollars lost. If a high-tier enterprise customer cancels, your revenue churn might be 10% even if your customer churn is only 1%. Since financial models project cash, revenue churn is the correct input.

How does ARPU influence strategy?

Knowing your ARPU dictates your acquisition channels. If your ARPU is $5 per month, you cannot afford an enterprise sales team; you need automated, low-touch marketing. If your ARPU is $5,000 per month, you can afford long sales cycles, dedicated account executives, and high customer acquisition costs.

Why did my MRR drop even though I got new customers?

This happens when your revenue churn exceeds your new revenue growth. For example, if you add ten new customers paying $10 a month (+$100 MRR), but two existing enterprise customers paying $100 a month cancel (-$200 MRR), your net MRR will decrease by $100, despite the higher total customer count.

Disclaimer: The information and calculators detailed in this article are provided for educational and informational purposes only. They do not constitute professional financial, accounting, or investment advice. Business operators should always consult with certified financial professionals or accountants to ensure accurate financial reporting and compliance with standard accounting principles (GAAP/IFRS).