MRR vs ARR: What They Are, How to Calculate Them, and Which to Use

MRR and ARR are the foundational revenue metrics for subscription businesses. They're also among the most frequently miscalculated and misrepresented metrics in SaaS. This guide covers the correct definitions, common errors, and when to use each.

The Correct Definitions

MRR (Monthly Recurring Revenue): The normalized monthly revenue from active subscriptions. Not total revenue. Not cash collected. Not invoiced. Normalized.

ARR (Annual Recurring Revenue): MRR × 12. For companies with annual contracts, ARR is the annualized value of the current subscription base.

The key word: recurring. One-time fees, professional services, setup fees, and usage overages (unless recurring) are excluded from both metrics.

How to Calculate MRR Correctly

Basic formula:

MRR = Σ(active subscriptions × monthly price)

Normalization rules:

• Annual plan at $1,200/year → $100 MRR (not $1,200)
• Monthly plan at $49/month → $49 MRR
• Semi-annual plan at $500 → $83.33 MRR ($500 ÷ 6)

What to exclude:

• One-time implementation fees
• Professional services revenue
• Usage overages (unless contracted minimum)
• Pilot/trial periods (until converted)

The 5 MRR Components

Healthy SaaS dashboards break MRR into components:

Net New MRR formula: Net New MRR = New MRR + Expansion MRR - Contraction MRR - Churned MRR

MRR vs ARR: When to Use Each

Rule of thumb:

• Pre-Series A: track MRR (more granular, more actionable)
• Series A+: convert to ARR for investor communication

Common MRR Calculation Errors

Error 1: Including non-recurring revenue

Wrong: $50K monthly MRR + $20K one-time implementation fees = "$70K MRR"

Correct: $50K MRR. The $20K is services revenue, tracked separately.

Error 2: Annual plan timing

Wrong: Company sells $12,000 annual plan in January → reports "$12,000 MRR" in January

Correct: $1,000 MRR normalized monthly. The $12,000 goes in deferred revenue on the balance sheet.

Error 3: Mixing contracted and realized

Wrong: Customer signs 3-year contract for $100K/year → "$300K ARR"

Correct: $100K ARR (one year's contracted amount). Multi-year contracts are booked at single-year ARR unless you track TCV separately.

Error 4: Counting trials

Wrong: 50 trial users × $99/month = "$4,950 MRR"

Correct: $0 MRR until the trial converts to paid.

The ARR Bridge: Communicating Growth

For board and investor updates, the ARR bridge is the standard format:

Beginning ARR:     $2,400,000
+ New ARR:           +$480,000
+ Expansion ARR:     +$240,000
- Contraction ARR:    -$60,000
- Churned ARR:       -$120,000
= Ending ARR:      $2,940,000

Net New ARR:         +$540,000
ARR Growth:          +22.5%

This format immediately communicates growth quality — the ratio of expansion to churn signals product-market fit strength.

Rule of 40 and ARR

The Rule of 40 (growth rate + profit margin ≥ 40) uses ARR growth rate:

Companies above 40 typically receive significantly higher valuation multiples regardless of absolute growth rate.

Use the SaaS MRR Calculator to track your MRR components and project ARR growth.