mkurman Key principles
MRR is the atomic unit - Every SaaS metric derives from Monthly Recurring Revenue. Get MRR calculation right first - it must exclude one-time fees, professional services, and usage overages. All other metrics (ARR, churn, LTV, NRR) build on top of a clean MRR number.
Churn compounds relentlessly - A 3% monthly churn rate sounds small but means losing 31% of customers annually. Always annualize churn when communicating to stakeholders, and always separate logo churn (customer count) from revenue churn (dollar amount) - they tell different stories.
Cohort over aggregate - Aggregate metrics hide trends. A stable overall churn rate can mask worsening retention in recent cohorts offset by strong early cohorts. Always build cohort views before drawing conclusions about retention or expansion.
Unit economics must be fully loaded - CAC must include all sales and marketing spend (salaries, tools, ads, content, events), not just ad spend. LTV must use gross margin, not revenue. Partial calculations give false confidence.
Board metrics need context, not just numbers - A number without a trend, benchmark, or explanation is noise. Every board metric should show: current value, period-over-period change, trailing trend (3-6 months), and a one-line narrative explaining why.
Core concepts
MRR waterfall is the movement model that explains how MRR changes month to month. Starting MRR + New MRR + Expansion MRR - Contraction MRR - Churned MRR = Ending MRR. This waterfall is the single most important operational view because it isolates growth drivers from retention issues.
Revenue retention comes in two flavors. Gross Revenue Retention (GRR) measures dollar retention excluding expansion - it can never exceed 100% and shows the floor of your revenue base. Net Revenue Retention (NRR) includes expansion and can exceed 100%, meaning existing customers grow faster than others leave. NRR above 120% is considered elite for B2B SaaS.
Unit economics connect acquisition cost to customer value. CAC (Customer Acquisition Cost) is total sales + marketing spend divided by new customers acquired. LTV (Lifetime Value) is ARPA times gross margin divided by revenue churn rate. The LTV:CAC ratio indicates efficiency - below 3:1 means unprofitable acquisition, above 5:1 may signal underinvestment in growth. CAC Payback Period (months to recover CAC from gross profit) is often more actionable than LTV:CAC because it avoids long-horizon LTV assumptions.
Cohort analysis groups customers by their signup month (or quarter) and tracks a metric (retention, revenue, usage) over time relative to their start date. The cohort table has signup periods as rows, months-since-signup as columns, and the tracked metric as cell values. Reading down a column shows whether newer cohorts perform better or worse than older ones.
Common tasks
Calculate MRR and ARR
MRR = sum of all active subscriptions normalized to monthly amounts. Annual contracts must be divided by 12. Exclude one-time charges, usage overages, and professional services.
Formula:
MRR = SUM(monthly_subscription_values for all active customers)
ARR = MRR * 12
MRR waterfall breakdown:
New MRR = MRR from customers acquired this month
Expansion MRR = MRR increase from existing customers (upgrades, seat adds)
Contraction MRR = MRR decrease from existing customers (downgrades)
Churned MRR = MRR lost from customers who cancelled
Net New MRR = New + Expansion - Contraction - Churned
Ending MRR = Starting MRR + Net New MRR
Always reconcile: Starting MRR + Net New MRR must equal Ending MRR. If it doesn't, there's a data issue (usually mid-month plan changes or proration).
Calculate churn rates
Separate logo churn (customers lost) from revenue churn (dollars lost).
Logo churn rate:
Monthly Logo Churn = Customers lost this month / Customers at start of month
Annual Logo Churn = 1 - (1 - Monthly Logo Churn)^12
Gross revenue churn rate:
Monthly Revenue Churn = (Contraction MRR + Churned MRR) / Starting MRR
Net revenue churn rate (can be negative if expansion exceeds churn):
Net Revenue Churn = (Contraction + Churned - Expansion) / Starting MRR
Never use ending-period denominators for churn. Use start-of-period or average-period customer/revenue counts. Ending-period denominators systematically understate churn because they exclude the customers who left.
Calculate LTV and CAC
Customer Acquisition Cost:
CAC = Total Sales & Marketing Spend / New Customers Acquired
(over the same period, typically monthly or quarterly)
Include in S&M spend: salaries, commissions, ad spend, content production, tools, events, agency fees. Exclude product costs and general overhead.
Lifetime Value (simple formula):
LTV = ARPA * Gross Margin % / Monthly Revenue Churn Rate
Where:
ARPA = Average Revenue Per Account (MRR / active customers)
LTV:CAC ratio and payback period:
LTV:CAC Ratio = LTV / CAC
CAC Payback (mo) = CAC / (ARPA * Gross Margin %)
The simple LTV formula assumes constant churn and no expansion. For businesses with strong NRR (>110%), use cohort-based LTV instead: sum the actual cumulative gross profit per cohort over 24-36 months.
Build a cohort retention table
A cohort table tracks how a group of customers (signed up in the same month) retains over time.
Table structure:
Month 0 Month 1 Month 2 Month 3 ...
Jan 2025 100% 88% 82% 78%
Feb 2025 100% 85% 79% -
Mar 2025 100% 90% - -
How to build from raw data:
- Assign each customer a cohort based on their signup month
- For each cohort, count active customers (or sum MRR) at each month-end
- Divide each cell by the Month 0 value to get retention percentage
- Read across rows for individual cohort trajectories
- Read down columns to compare cohort quality over time
Revenue cohort (shows dollar retention including expansion):
- Same structure but cells contain MRR rather than customer count
- Cells can exceed 100% if expansion outpaces churn (shows NRR by cohort)
The most common mistake is using calendar months instead of relative months. Month 1 means "one month after signup", not "the next calendar month." A customer who signs up Jan 28 and is measured Feb 1 has not completed Month 1.
Calculate net revenue retention (NRR)
NRR measures dollar-for-dollar how much revenue you retain and grow from existing customers over a period.
Monthly NRR:
NRR = (Starting MRR - Contraction - Churned + Expansion) / Starting MRR
Annual NRR (trailing 12-month):
Annual NRR = MRR from customers who were active 12 months ago / Their MRR 12 months ago
The trailing 12-month version is preferred for board reporting because it smooths monthly volatility. Calculate it by taking the set of customers active at the start of the 12-month window and comparing their current MRR to their starting MRR.
NRR above 100% means the business grows even with zero new customers. Median NRR for public SaaS companies is approximately 110-115%. Top quartile exceeds 125%.
Calculate SaaS Quick Ratio
The Quick Ratio measures growth efficiency by comparing revenue added to revenue lost.
Quick Ratio = (New MRR + Expansion MRR) / (Contraction MRR + Churned MRR)
- Quick Ratio > 4: Very efficient growth (adding $4 for every $1 lost)
- Quick Ratio 2-4: Healthy growth
- Quick Ratio < 2: Leaky bucket - churn is undermining growth efforts
Quick Ratio is most useful for early/mid-stage companies. At scale, absolute NRR and net new MRR matter more than the ratio.
Prepare a board metrics deck
A board deck should present metrics in a consistent, scannable format. Use this standard structure for the financial/metrics section:
Slide 1 - Headline KPIs (single slide, 4-6 metrics):
| Metric | Current | MoM Change | QoQ Change | Target |
|---------------------|----------|------------|------------|--------|
| ARR | $4.2M | +3.1% | +9.8% | $4.5M |
| Net New MRR | $38K | +12% | +22% | $35K |
| Logo Churn (mo) | 2.1% | -0.3pp | -0.8pp | <2.5% |
| NRR (trailing 12mo) | 118% | +2pp | +5pp | >115% |
| CAC Payback (mo) | 14 | -1 | -3 | <18 |
| Customers | 312 | +18 | +48 | 330 |
Slide 2 - MRR Waterfall (stacked bar chart): Show New, Expansion (positive), Contraction, Churned (negative) for past 6 months.
Slide 3 - Cohort Retention (heatmap table): Show last 6-8 monthly cohorts with revenue retention at Month 1, 3, 6, 12. Color-code: green >90%, yellow 80-90%, red <80%.
Slide 4 - Unit Economics: LTV, CAC, LTV:CAC, Payback Period with trailing 3-month averages.
Always use the same metric definitions across board decks. Define each metric in a glossary appendix slide so board members share a common language. Change in methodology mid-stream destroys trust.
See references/board-reporting.md for a full board deck template with chart
specifications and narrative frameworks.
Anti-patterns / common mistakes
| Mistake | Why it's wrong | What to do instead |
|---|---|---|
| Counting contracted ARR as MRR * 12 | Contracted ARR includes unsigned pipeline; MRR * 12 is recognized recurring revenue only | Use MRR * 12 for ARR; track contracted ARR separately |
| Mixing logo churn and revenue churn | A few large customers churning can show low logo churn but devastating revenue churn | Always report both; segment by customer size |
| Using revenue instead of gross margin in LTV | LTV should reflect profit, not top-line revenue; ignoring COGS overstates LTV by 20-40% | LTV = ARPA * Gross Margin % / Churn Rate |
| Reporting only aggregate retention | Aggregate retention hides cohort deterioration when early cohorts are sticky and recent ones are not | Build monthly cohort tables and report cohort curves |
| Annualizing one bad/good month | A single month of 5% churn does not mean 46% annual churn - it could be an anomaly | Use trailing 3-month or 6-month averages for annualized rates |
| Excluding some S&M costs from CAC | "Blended CAC" that excludes salaries or content costs gives a falsely attractive picture | Fully loaded CAC includes all S&M spend: people, tools, ads, events |
| Changing metric definitions between boards | Board members lose trust when numbers aren't comparable period-to-period | Lock definitions in a glossary; if methodology changes, restate historicals |
Gotchas
Ending-period denominator used for churn calculation - Using the end-of-period customer count in the denominator systematically understates churn because churned customers are excluded from the denominator. Always use the start-of-period (or average-period) count.
Revenue churn calculated from revenue instead of gross margin - LTV must use gross margin, not revenue. A customer paying $1000/month with 60% gross margin has half the LTV of the raw revenue number. Using revenue LTV overstates CAC payback attractiveness.
MRR including one-time or non-recurring charges - Professional services revenue, setup fees, and annual true-ups included in MRR inflate the number and create a misleading growth signal. MRR must contain only normalized recurring subscription revenue. Audit your MRR data source definition before reporting.
Cohort table using calendar months instead of relative months - Month 1 means "one month after signup," not "the next calendar month." A customer who signs up January 28 and is measured February 1 has not completed Month 1. Calendar-based cohort tables produce meaningless curves for businesses with mid-month signups.
Board metrics changed mid-stream without restating historicals - Changing the definition of a metric between board meetings (e.g., how churn is calculated) makes trend comparisons meaningless and erodes investor trust. Always lock definitions in a glossary. If methodology must change, restate at least 12 months of historicals.
References
For detailed content on specific sub-domains, read the relevant file from
references/:
references/metric-formulas.md- Complete formula reference for all SaaS metrics with edge cases, pro-rata handling, and multi-currency considerations. Load when calculating specific metrics from raw data.references/cohort-analysis.md- Step-by-step cohort table construction, visualization techniques, revenue vs. logo cohorts, and interpreting cohort curves. Load when building or analyzing cohort data.references/board-reporting.md- Full board deck template, chart specs, narrative frameworks, benchmark tables, and investor FAQ responses. Load when preparing a board deck or investor update.
Only load a references file if the current task requires deep detail on that topic.
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