If you run a subscription business, ARR is the scoreboard. But the way you build and maintain your ARR calculator determines whether it’s a precision instrument or a pretty lie. Let’s walk through three levels: manual workflows, no-code automation, and finally scaling with an AI agent.## 1. Traditional Manual Workflows (Google Sheets & Excel)### 1.1 Build a basic ARR calculator in Google Sheets1. Open a new Sheet and create columns: `Month`, `MRR`, `New MRR`, `Expansion MRR`, `Churned MRR`, `Net New MRR`, `ARR`.2. Enter historical monthly values for MRR and its components (from Stripe, Chargebee, your CRM, or accounting system).3. In `Net New MRR` (say cell F2), use a formula like: `=C2 + D2 - E2` 4. In `MRR` for the current month, calculate: `=B1 + F2` (last month’s MRR + Net New MRR). Copy down.5. In `ARR`, use the standard formula from SaaS finance: `=B2*12` (MRR × 12) or, if you have annual contracts tracked separately, use: `=B2*12 + Annual_Contracts_Cell`.6. Add a total ARR cell at the top: `=INDEX(G:G, MATCH(MAX(A:A), A:A, 0))` to always pull the latest month’s ARR.7. For more on formulas in Sheets, see Google’s guide: https://support.google.com/docs/answer/3094282### 1.2 Build a structured ARR model in Excel1. In Excel, mirror the same headers on a worksheet: `Month`, `MRR`, `New ARR`, `Expansion ARR`, `Churn ARR`, `Net New ARR`, `Total ARR`.2. If you’re working directly in ARR (annualized) instead of MRR, follow the Wall Street-style formula: `ARR = Previous ARR + Gross New ARR + Expansion ARR + Reactivation ARR − Contraction ARR − Churn ARR`.3. In `Net New ARR` (F2): `=C2 + D2 + Reactivation_ARR - Contraction_ARR - E2`.4. In `Total ARR` (G2): `=G1 + F2`.5. Use absolute references for key assumptions (e.g., churn rates) so you can tweak them easily.6. Turn your data into a table and chart ARR over time using Insert → Charts. See Microsoft’s formula overview: https://support.microsoft.com/office/overview-of-formulas-in-excel-ecfdc708-9162-49e8-b993-c311f47ca173### 1.3 Manual data import from billing tools1. Export monthly revenue reports from Stripe/Chargebee as CSV.2. In Sheets: File → Import → Upload → select CSV → insert to new sheet.3. In Excel: Data → Get Data → From Text/CSV → load into your ARR workbook.4. Use VLOOKUP or INDEX/MATCH to map raw data into your ARR model.**Pros (manual):** Full control, good for learning the mechanics of ARR. **Cons:** Time-consuming, error-prone, easy to forget updates before a board meeting.## 2. No-Code Automation with Google Sheets & Excel### 2.1 Automate ARR inputs to Google Sheets1. Use Zapier, Make, or a similar tool to connect Stripe/PayPal/your CRM to Google Sheets.2. Create a Zap like: “New successful charge in Stripe → Append row in Google Sheets”.3. Store each transaction (date, amount, customer, plan) in a raw data sheet.4. On your ARR sheet, use `QUERY`/`SUMIF` to aggregate by month and plan: `=SUMIF(Raw!A:A, =A2, Raw!B:B)` to sum revenue for that month.5. From monthly MRR, compute ARR using `=MRR*12` and track new, expansion, and churned MRR using categorized transactions.6. Learn how to use functions like SUMIF in Sheets: https://support.google.com/docs/answer/3093480### 2.2 Refresh ARR in Excel using Power Query1. Save your billing export or database view in a consistent folder.2. In Excel, go to Data → Get Data → From File (or From Database) and use Power Query to load and transform the data.3. Clean columns (customer, plan, amount, start/end date) and load them into an `ARR_Raw` table.4. In your ARR model sheet, use `SUMIFS` to aggregate monthly recurring amounts and derive MRR/ARR.5. Click Data → Refresh All to update ARR as new data lands.6. More on creating formulas and linked models: https://support.microsoft.com/office/create-a-formula-that-refers-to-values-in-other-cells-56c40419-66bc-48b2-8e72-83e78c09f53f### 2.3 Scheduled dashboards1. In Google Sheets, connect your ARR sheet to Looker Studio or create charts directly in Sheets.2. In Excel, build charts on top of the ARR table and save as a dashboard tab.3. Use no-code tools to send a weekly PDF of ARR charts to your leadership or clients.**Pros (no-code):** Less manual work, more reliable updates, still transparent. **Cons:** Integrations can break when schemas change; you’re still the one wiring everything together.## 3. Scaling ARR with an AI Computer Agent (Simular)This is where you stop being the spreadsheet operator and become the architect. A Simular Pro AI computer agent behaves like a power user sitting at your machine.### 3.1 Agent to maintain ARR in Google Sheets**Workflow:**1. The agent opens your browser, logs into Stripe, and downloads the latest revenue CSV.2. It opens Google Sheets, finds the ARR workbook, and imports the CSV into the raw data tab.3. It checks that key formulas (MRR, ARR, Net New ARR) exist and extends them down new rows.4. It updates ARR charts and writes a short summary in a notes tab: “ARR grew 8% MoM; churn ARR was $12,400; expansion ARR offset 110% of churn.”**Pros:** No integration setup, works with any billing tool or CRM UI, and every step is visible and editable. **Cons:** Requires a clear playbook the first time and a stable UI layout.### 3.2 Agent to synchronize Excel models and investor packets**Workflow:**1. On a schedule, the agent opens your desktop Excel ARR model.2. It refreshes Power Query connections, waits for recalculation, and checks that key cells (Total ARR, Net New ARR) are updated.3. It copies charts into a pitch deck or monthly investor update doc.4. It exports a PDF pack to a shared folder or emails it via your preferred email client.**Pros:** Perfect for finance teams who live in Excel and PowerPoint; zero repetitive exporting or copy-paste. **Cons:** Best on a stable finance workstation; heavy models may require tuning agent steps.### 3.3 Agent to reconcile ARR across tools**Workflow:**1. The agent logs into your CRM, billing system, and accounting tool.2. It exports customer and revenue lists, compares them in Sheets or Excel, and flags mismatches (e.g., customers active in CRM but not billed). 3. It writes a reconciliation report, highlighting suspicious churn or missing invoices.**Pros:** Catches revenue leaks and data quality issues that manual or no-code flows often miss. **Cons:** Initial setup is more involved, but once configured, it scales to thousands of accounts.At this third level, you’re not just calculating ARR—you’re delegating the entire workflow. Google Sheets and Excel remain your modeling canvas. The AI computer agent becomes the operator that tirelessly feeds, maintains, and audits those models while you use the insights to steer the business.

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