MRR Churn Forecaster: Project Your SaaS Revenue Month by Month

How This Tool Works

The forecast starts with your current MRR and applies four forces each month: existing MRR carries forward reduced by gross churn, expansion revenue adds from upsells and seat growth, net-new MRR arrives from new customers, and the result becomes the next month's starting balance. The formula per month is: End MRR = Start MRR × (1 - gross churn) × (1 + expansion rate) + new MRR This structure separates existing-customer behavior from acquisition, which is crucial because churn and expansion both happen inside the base. Losing five customers and upselling three others is not the same as losing five and acquiring none. The tool also calculates annualized NRR using the formula: (1 - gross churn + expansion rate) ^ 12. If your monthly gross churn is 4% and expansion is 1%, your annualized NRR is (1 - 0.04 + 0.01)^12 = 0.97^12 = 69%. This means your existing customer base shrinks 31% in revenue terms each year, and you need new sales just to offset that decline and keep flat. You can also overlay a zero-churn line on the forecast to see exactly how much compounding cost the churn imposes over your forecast horizon. A small monthly rate - say 3% - looks manageable in isolation, but compounds into a large revenue gap when you project it over two years.

How to Use the Calculator

The inputs are five fields: 1. Starting MRR - the recurring revenue you began the month with. Include all subscription revenue, not just new sales. 2. Monthly Churn Rate - the share of current MRR you lose each month to cancellations and downgrades. As a decimal, 3% is 0.03. 3. Monthly Expansion Rate - the share of current MRR that comes from upgrades, seat expansion, and reactivations of existing customers. This is usually lower than churn, but can exceed it. 4. New MRR per Month - the fixed monthly recurring revenue your acquisition adds. This assumes consistent acquisition, not a ramping or declining sales pipeline. 5. Forecast Months - how many months to project forward, from 12 to 36. The chart updates immediately as you change any input. The final MRR row shows the projected revenue at the end of the forecast period. The NRR row shows what percent of current MRR your base retains through expansion alone. The table below the chart shows month-by-month detail: starting balance, MRR lost to churn, MRR added by expansion, new MRR, and ending balance for each month.

When to Use This Tool

Use this calculator when: - You are modeling cash flow or hiring plans. A single-month churn percentage tells you what happened last month. A forecast tells you whether the business needs more acquisition, whether you should reduce burn, or whether the revenue curve can support your current cost structure. Founders who tie owner compensation or contractor budgets to revenue forecasts need this level of detail. - You want to test "what-if" scenarios without a spreadsheet. Toggling your churn rate from 3% to 2% and watching the 24-month outcome change is faster than rebuilding a spreadsheet formula. You can quickly see whether a specific churn improvement is worth a retention hire or whether new sales growth is the only realistic lever. - You are pitching investors or explaining unit economics. A forecast separates the three components of SaaS growth (churn, expansion, and acquisition) and makes it clear why each one matters. An investor who sees that your net-new bookings barely cover churn will ask better questions than one who only sees top-line growth. - You need to understand the cost of churn visually. The zero-churn overlay shows the exact revenue gap between your current model and a hypothetical zero-churn version. For many teams, this gap is larger than expected and changes how they prioritize retention work.

Interpreting Your Results

NRR below 70%: Your existing customer base is shrinking faster than it grows from expansion. You need strong new customer acquisition to keep the business flat. NRR between 70-100%: Your base is stable but not growing. Expansion revenue is meaningful but does not offset churn entirely. Growth depends on new sales. NRR above 100%: Your existing customers generate more revenue through expansion than you lose to churn. This is the most efficient business state. Even if acquisition slows, the base grows on its own. Only enterprise and land-and-expand SaaS models typically reach this state at scale. Growth ceiling in the forecast: This is the month where new MRR equals churned MRR. After that month, growth stalls unless you improve churn, increase expansion, or add more new bookings. If the ceiling appears within 6-12 months, it signals that current unit economics do not support indefinite growth. The zero-churn gap: Subtract the zero-churn curve from your actual forecast at month 24. If the gap is $20,000 MRR or more, churn is your largest hidden cost. Reducing churn by 1% point is often worth more than a 10% acquisition increase.

Common Forecasting Patterns

The flat growth pattern: Churn and new bookings are nearly equal, expansion is small. The curve stays flat. This is a common state for early-stage products with strong acquisition but weak retention. Growth only accelerates if retention improves or new sales increase. The declining pattern: Churn exceeds new bookings plus expansion. The curve trends downward. This state is unsustainable and signals that retention or acquisition needs immediate attention. If you see this in a forecast, the business is not stable at the current unit cost. The compounding pattern: Expansion is large relative to churn, and new bookings are consistent. The curve steepens over time. This is the target pattern and is common in later-stage SaaS with strong land-and-expand dynamics and improving retention.

Example Forecast

Start MRR: $50,000. New MRR per month: $5,000. Monthly gross churn: 4%. Monthly expansion: 1%. Run the forecast for 24 months. Month 1: Start $50,000, after 4% churn = $48,000, after 1% expansion = $48,480, plus $5,000 new = $53,480. Month 12: Following the same pattern forward, MRR reaches approximately $94,000. NRR is 69%, meaning the existing base shrinks 31% per year. Month 24: MRR reaches approximately $150,000. If you toggle the zero-churn overlay, the same business reaches $170,000 at month 24. The $20,000 gap is the compounding cost of 4% monthly churn. This is the key insight: churn does not only reduce this month's revenue. It removes revenue that could have expanded next month and the month after that. A small monthly rate compounds into a large annual drag on the forecast.

Frequently Asked Questions