MRR vs ARR: What SaaS Founders Actually Need to Track

Every SaaS founder tracks MRR. Far fewer track it correctly. And the difference between tracking it correctly and approximately has consequences that compound over time — in your financial model, your investor conversations, and your strategic decisions.

The Simple Definition

MRR (Monthly Recurring Revenue) is the normalised monthly value of all active recurring subscription contracts. It answers the question: how much predictable revenue does this business generate every month?

ARR (Annual Recurring Revenue) is MRR multiplied by 12. It annualises your recurring revenue to give a larger-scale view — and it's the metric most commonly used when discussing valuation, fundraising targets, and business milestones.

That's the simple version. The complexity — and the mistakes — live in the details.

How to Calculate MRR Correctly

MRR is normalised monthly recurring revenue. The "normalised" part is where most founders go wrong.

Annual contracts

A customer paying £12,000 per year contributes £1,000 to MRR — not £12,000 in the month they pay. Always divide annual and multi-year contract values by the number of months in the contract term.

Monthly contracts

A customer paying £500 per month contributes £500 to MRR. Straightforward — but remember to include all active subscriptions, not just the ones that renewed this month.

What not to include in MRR

• One-time setup or implementation fees
• Professional services or consulting revenue
• Variable usage charges (unless they recur predictably)
• Trial subscriptions that haven't converted to paid
• Paused or suspended subscriptions

The Four Components of MRR Movement

Tracking a single MRR number is a starting point. The real insight comes from understanding what's driving that number — and what's changing it month to month.

Net New MRR = New MRR + Expansion MRR − Contraction MRR − Churned MRR

A business growing MRR at 10% per month through new customer acquisition only looks healthy. A business growing at the same rate with strong expansion and low churn is fundamentally different — and more valuable, because the existing customer base is compounding rather than just being replaced.

When to Use MRR vs ARR

Both metrics are measuring the same underlying thing — recurring revenue — just at different scales. The right one to use depends on context:

ARR Milestones That Matter

ARR milestones have become reference points in the SaaS funding landscape — not hard rules, but widely-used shorthand for stage readiness.

• £100k ARR: Proof that someone is willing to pay. Often the threshold for pre-seed institutional investment.
• £500k ARR: Early traction — repeatable sales motion starting to emerge. Seed stage territory.
• £1M ARR: "The first comma." Widely cited as the milestone that makes Series A conversations meaningful.
• £3M ARR: Strong Series A candidate in the current UK/EU market, assuming healthy growth rate.
• £10M ARR: Series B territory. Suggests scalable go-to-market and expanding market penetration.
• £30M ARR: Growth stage. The business is at scale — the question now is efficiency and path to profitability.

These milestones are reference points, not gates. A business at £800k ARR growing 20% month-on-month with strong NDR will get more investor attention than a business at £1.2M ARR growing 5%. Stage is about trajectory, not just the number.

The Most Common MRR Mistakes

Mistake 1: Including annual contract value in the month it's paid

If a customer pays £12,000 upfront for an annual contract in January, your MRR for January is £1,000 — not £12,000. Recording it as £12,000 artificially inflates January MRR and creates a cliff in February that looks like churn but isn't.

Mistake 2: Not tracking MRR at the right point in time

MRR should be calculated at a consistent point — typically end of month, or a consistent date within the month. Calculating it at different times in different months introduces noise that makes month-on-month comparisons unreliable.

Mistake 3: Conflating cash receipts with MRR

Cash can arrive before the subscription period starts (annual contracts paid upfront) or after (failed payments, delayed processing). MRR reflects the subscription value for the period — not when cash was received.

Mistake 4: Not separating trial from paid

Free trials don't contribute to MRR. Extended trials at heavily discounted rates should be tracked separately. Including them inflates MRR and obscures true conversion performance.

Mistake 5: Ignoring expansion and contraction

Tracking only new customers and cancellations misses the expansion and contraction signals that often contain the earliest warnings about product health and pricing architecture. If contraction MRR is rising, something is wrong with how customers are experiencing value — and it will show up in churn six months before churn starts climbing.

What Investors Look For Beyond the Number

When an investor asks "what's your MRR?", they're starting a conversation, not ending one. The number opens the door — the analysis behind it determines whether the conversation continues.

Be prepared to explain: the MRR movement breakdown (new, expansion, contraction, churn), the growth rate over the last 3, 6, and 12 months, the trend direction (accelerating, stable, or decelerating), how your metrics benchmark against industry comparables, and the cohort analysis that shows retention quality over time.

All of this requires having your data unified, current, and accessible — not assembled from four different sources the night before a pitch. VentureDeck calculates every component of MRR automatically from your Stripe data, benchmarks it against your industry, and keeps everything updated in real time. When an investor asks the question, you send the link.