MRR: the single most important SaaS metric
Monthly recurring revenue is the heartbeat of any subscription business. Unlike one-time revenue, which bounces around with promotions and seasonality, MRR is a clean, forward-looking measure of how much money the business will collect next month assuming no one leaves. It is also the baseline from which every other SaaS metric (ARR, NRR, LTV, payback) is derived.
The formula is Net New MRR = New MRR + Expansion MRR − Churn MRR. The calculator above shows how each of those components combines into a monthly growth rate, and projects MRR and implied ARR 24 months forward. It is a simple model — no cohorts, no seasonality — but it is the right mental model for any founder who needs to understand where their business is heading.
The four MRR movement categories
- New MRR: first-time subscriptions from new customers.
- Expansion MRR: existing customers upgrading plans or adding seats.
- Contraction MRR: existing customers downgrading.
- Churn MRR: customers canceling entirely.
Most finance dashboards combine expansion and new into "gross new MRR" and combine churn and contraction into "gross churn MRR." The calculator above treats expansion as a separate input because it is often the fastest-growing lever in a maturing business and should be modeled explicitly.
ARR vs MRR — and why both matter
Annual recurring revenue is just MRR × 12. Investors quote in ARR because it is bigger and sounds more meaningful. Founders run operations in MRR because that is the speed the business moves at. Board decks typically show both. When people say "SaaS companies with $1M ARR," that is roughly $83K MRR.
Healthy growth rates by stage
- $0–10K MRR: 20%+ month-over-month is possible and expected.
- $10–100K MRR: 10–20% MoM is strong.
- $100K–1M MRR: 5–10% MoM is the venture "triple, triple, double, double" path.
- $1M+ MRR: 3–5% MoM (45–80% annualized) is strong at scale.
- $10M+ MRR: 2–3% MoM is still excellent.
Growth rate decelerates as you get larger — not because you are losing efficiency but because the law of large numbers catches up. A 50% growth rate on $100K MRR is $50K of new MRR per month. Same percentage growth at $10M MRR requires $5M in new MRR monthly, which is hard in any category.
Expansion is the growth engine of mature SaaS
In the early days, new logos drive growth. In mature SaaS businesses, expansion from existing customers is often 40–60% of net new MRR. This is why "land and expand" is the right go-to-market for B2B: start with a small wedge, grow revenue per account via seats, usage, and upsell. Best-in-class businesses hit NRR (net revenue retention) of 110–130%, meaning expansion alone outgrows churn.
Rule of 40
For SaaS benchmarking, the Rule of 40 says Growth Rate + Profit Margin ≥ 40%. A business growing at 60% per year with −20% margin passes. A business growing at 20% with 20% profit margin passes. Anything below 40% signals inefficient growth. For sub-scale small businesses the rule is less useful, but past $1M ARR it is the benchmark used by investors when they underwrite a company.
Modeling tradeoffs in the calculator
Play with the inputs to see how different strategic choices affect trajectory. Two common levers:
- Cut churn in half. A 4% monthly churn dropped to 2% typically raises 12-month MRR by 40–60% at the same acquisition pace — because you keep the customers you paid to acquire.
- Add expansion. $500/month of incremental expansion MRR compounds into $40K+ additional MRR over 24 months.
The leverage of retention and expansion is always larger than new-customer acquisition for any business past its first few hundred customers.
MRR pitfalls — the numbers you must exclude
MRR is a pure monthly recurring metric. Do not include:
- One-time setup fees or professional services.
- Annual prepayments (include 1/12 of the annual amount each month, not the lump sum).
- Non-recurring add-ons.
- Discounts in the gross number — use net billed, not list price.
Mixing these in inflates MRR and creates misleading trajectories. Separate one-time revenue on its own line so your MRR trend reflects only the recurring base.
Put the numbers to work
Combine this calculator with the churn rate calculator to understand retention specifically, the LTV calculator to size customer economics, and the cash flow calculator to translate MRR into bank-account dollars. The four together give you a complete SaaS finance stack for weekly operating decisions.