How to Build an ARR Bridge from a CSV Export
What Is an ARR Bridge?
An ARR bridge (also called an ARR waterfall) reconciles your Annual Recurring Revenue from one period to the next by breaking the change into five components: Beginning ARR, New Business, Expansion, Contraction, and Churn — arriving at Ending ARR.
Formula: Ending ARR = Beginning ARR + New Business + Expansion − Contraction − Churn
It's the standard format for SaaS board reporting because it shows exactly why ARR moved — not just the net change.
What Your CSV Needs
To build an ARR bridge from a CSV export, you need one row per customer per month with at minimum:
- Customer identifier — name or ID
- Period — month and year (e.g. 2026-01)
- ARR value — the customer's ARR for that month
Most CRMs and billing systems can produce this export in under five minutes. In Salesforce, it's a subscription or opportunity report. In HubSpot, it's a deals export filtered by recurring revenue. In Chargebee or Recurly, it's the MRR export converted to ARR.
How ARR Bridge Movements Are Classified
Once you have customer-level ARR by period, the bridge is built by comparing each customer's ARR month-over-month:
- New Business — customer appears for the first time (prior month ARR = 0, current month ARR > 0)
- Expansion — existing customer's ARR increased (current > prior, both > 0)
- Contraction — existing customer's ARR decreased (current < prior, both > 0)
- Churn — existing customer's ARR went to zero (prior > 0, current = 0)
- Reactivation — previously churned customer returns (prior = 0, current > 0, but customer existed before)
The contraction vs. churn distinction is critical. A customer who reduces from $60K to $20K has contracted $40K — that's not churn. Misclassifying contraction as churn overstates logo churn and understates GRR.
Calculating GRR and NRR from the Bridge
Once you have the bridge components, GRR and NRR follow directly:
GRR = (Beginning ARR − Churn − Contraction) ÷ Beginning ARR
NRR = (Beginning ARR − Churn − Contraction + Expansion) ÷ Beginning ARR
For TTM (trailing twelve month) versions, you sum the components across 12 months and divide by the Beginning ARR from 12 months ago. TTM smooths out monthly volatility and is the standard format for investor reporting.
The Manual Excel Approach (and Why It Breaks)
Building this in Excel requires VLOOKUP or INDEX/MATCH to compare each customer's ARR across periods, IF statements to classify movements, SUMIF to aggregate by category, and careful handling of edge cases like customers who churn and return. A complete ARR bridge model in Excel typically runs 8-12 tabs and takes several hours to build correctly.
The bigger problem is maintenance. Every month you add new data, the formulas need to extend, edge cases accumulate, and the risk of a formula error silently corrupting your metrics grows. Most teams end up with a model that "works" but that nobody fully trusts.
The Faster Path
ARRGuide takes your CSV export and does all of this automatically — classifying movements, building the bridge, calculating TTM and monthly GRR and NRR, and generating customer-level detail behind every number. Upload once and your board metrics are ready. Add a new month's data and everything recalculates instantly.
Works with exports from any system: Salesforce, HubSpot, Chargebee, Recurly, Zuora, QuickBooks, or a plain spreadsheet. No Stripe required, no integration setup, no formulas to maintain.
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