

Every SaaS story has the same scene: it’s the first week of the month, a founder or agency owner is hunched over Google Sheets and Excel, hunting for updated customer counts, copying Stripe exports, and trying to remember which column is churn and which is expansion.
An MRR calculator cuts through that chaos. By standardizing the formula (MRR = average revenue per account × active customers) and centralizing inputs, you get a single source of truth for growth, churn, and forecasts. It turns scattered invoices and CRM notes into a simple, comparable metric you can use in board meetings, sales standups, and marketing planning. Like the machining MRR examples, you define a clear formula and feed in the right dimensions: plan price, customer count, new, churned, expanded.
But the real leverage comes when an AI computer agent takes over the drudgery. Instead of you logging into billing tools, downloading CSVs, and massaging columns, the agent can open Google Sheets or Excel, pull the latest numbers from your browser or desktop apps, apply the MRR formulas, and refresh charts on a schedule. You stay focused on why the numbers are moving; the agent handles how they get calculated.
If you run a subscription business, your Monthly Recurring Revenue is the heartbeat of your company. Let’s walk through practical ways to build an MRR calculator—from fully manual to fully automated with an AI agent—so you can stop scrambling at month-end.
Month, Active Customers, ARPA, MRR.ARPA (Average Revenue Per Account), enter your subscription price (e.g., $49).Active Customers, enter the customer count for each month.MRR cell, use the formula:=B2*C2 (assuming B is customers, C is ARPA).Docs: Google Sheets formulas guide — https://support.google.com/docs/answer/3093480
Plan, Price, Customers.Total MRR cell, use:=SUMPRODUCT(B2:B5, C2:C5) (B = prices, C = customers).Churned Customers by plan and compute Churned MRR using another SUMPRODUCT.New MRR, Churned MRR, Net New MRR, Total MRR.
Insert > Table).Status column with a formula to check if the customer was active in a given month (e.g., using IF with start/cancel dates).Price for active customers by month. This gives you MRR by month directly from transactional data.Docs: Excel formulas overview — https://support.microsoft.com/en-us/office/create-a-formula-in-excel-ecfdc708-9162-49e8-b993-c311f47ca173
Customer ID, Plan, MRR, Status, Created At, Cancelled At to columns.SUMIFS, FILTER) to compute:New MRR (customers created this month).Churned MRR (customers cancelled this month).Expansion MRR (upgrades).Docs: Connect forms to Sheets — https://support.google.com/docs/answer/2917686
Data > Get Data).Docs: Excel data import basics — https://support.microsoft.com/en-us/office/import-and-analyze-data-66bf7ee6-2eaf-4d10-9d52-5b53b83bb8a6
Now imagine an AI agent that uses your computer like a smart assistant—opening the browser, logging into billing tools, exporting reports, and updating Sheets or Excel for you.
Story: Each month, instead of your ops lead doing the “MRR dance,” your Simular AI agent does it.
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When you combine solid spreadsheet models with an AI agent that can click, type, and calculate on your behalf, MRR moves from a painful monthly ritual to a continuous, reliable signal for every decision you make.
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Start by deciding what questions your MRR model must answer: overall MRR, new MRR, churned MRR, expansion MRR, and net new MRR. Then design your spreadsheet around those outputs.
Is Active This Month: uses a formula comparing Start/Cancel dates to the month you’re analyzing.Effective MRR: equals Price when active, 0 when not.SUMIFS / FILTER / PivotTables to compute:Keep all hard data in Raw Data and all logic in Summary. This separation makes it easier for you—or an AI agent—to maintain and extend the model.
When you have several plans, avoid hard-coding each price into every row. Instead, normalize your data and use lookup formulas.
Plan Code and use VLOOKUP/XLOOKUP (Excel) or VLOOKUP/INDEX-MATCH (Sheets) to pull the Monthly Price from the Plans table.=AnnualPrice/12).SUMIFS on Plan Code.SUMIFS.This structure is also easier for an AI agent to understand and manipulate, since pricing rules live in a single, well-labeled place.
Churn and expansion are where MRR becomes a strategic tool. To track both precisely:
Previous MRR, Current MRR, MRR Change, and Change Type.Current MRR. Use a formula like =CurrentMRR-PreviousMRR for MRR Change.Change Type using nested IF logic:Status changed from Active to Cancelled, label as Churn.MRR Change > 0 and still Active, label as Expansion.MRR Change < 0 and still Active, label as Contraction.SUMIFS to aggregate:New + Expansion − Churn − Contraction.This layout makes your revenue story explicit and lets a human or AI agent quickly build dashboards, reports, and alerts around the most important movements.
You can reduce the “export CSV, copy, paste” grind without writing code.
A2:A instead of A2:A500) so new rows are automatically included.This combination lets you keep your MRR logic where you’re comfortable while offloading the repetitive data sync work.
Treat your MRR workbook like production code and your AI agent like a junior analyst who can click very fast.
By combining spreadsheet best practices with transparent, inspectable agent runs, you keep control of your financial truth while delegating the tedious mechanics of keeping it up to date.