I've sat in enough forecast reviews to know that if you put ten SaaS finance leaders in a room and ask them to define an ARR Bridge, ARR Waterfall, and ARR Rollforward, you'll probably get twelve answers.
Most of those answers are probably right.
These terms get used interchangeably — sometimes correctly, sometimes not. Most of the confusion comes from the fact that everyone is trying to answer the same question:
What happened to ARR?
That's the real objective. The terminology comes second.
The ARR Rollforward
The ARR Rollforward is probably the most fundamental of the three.
It's simply a reconciliation between a beginning balance and an ending balance.
You start with ARR at the beginning of the period. Then you account for everything that changed it.
- New ARR
- Expansion ARR
- Contraction ARR
- Churned ARR
When you're finished, you arrive at ending ARR.
The rollforward's job is simple. Prove how you got from the starting number to the ending number.
If someone asks, "Why is ARR $22.4 million this month when it was $21.7 million last month?" the rollforward provides the answer.
The ARR Bridge
The ARR Bridge is usually the same underlying math presented differently.
Instead of focusing on reconciliation, it focuses on explanation. A bridge tells the story of movement.
You still start with beginning ARR. You still end with ending ARR. You still have New, Expansion, Contraction, and Churn in the middle.
The difference is that the bridge is designed for communication. This is why ARR Bridges show up in board decks so often.
A board member typically doesn't care that your numbers reconcile. They want to understand what drove the change. The bridge turns accounting movement into a business narrative.
The ARR Waterfall
This is where things get messy.
When most people say "ARR Waterfall," they mean one of two things. Sometimes they're talking about the exact same analysis as an ARR Bridge. Other times they're talking about the chart itself.
The waterfall chart has become one of the most common ways to visualize ARR movement because it shows contributions clearly. Beginning ARR sits on the left. Ending ARR sits on the right. Everything that increased or decreased ARR appears in between.
Because of that, many finance teams use "ARR Bridge" and "ARR Waterfall" interchangeably. One is describing the analysis. The other is describing the visualization.
So Which One Is Correct?
Honestly, all of them.
If someone says ARR Rollforward, I know they're talking about reconciliation. If someone says ARR Bridge, I know they're talking about explaining movement. If someone says ARR Waterfall, I usually assume they're talking about the chart.
But underneath all three is the same concept: ARR moved, something caused that movement, and we need to explain it.
The Real Problem Isn't the Terminology
Finance teams rarely spend much time arguing about definitions. They spend a lot of time arguing about numbers.
One report says Expansion ARR was $300,000. Another says $420,000. Someone pulls Salesforce. Someone exports from the ERP. Someone updates a spreadsheet. Now everyone is debating the output instead of discussing the business.
I've seen this happen at every SaaS company I've worked with. The issue is almost never the bridge. The issue is almost never the waterfall chart. The issue is that there isn't agreement on the underlying movement.
Start With the Movement
I've become convinced that the most important part of ARR reporting isn't the rollforward, bridge, or waterfall. It's the event that caused the movement in the first place.
A renewal happened. A customer expanded. A contract was downsized. A customer churned.
Once those movements become the source of truth, everything else becomes much easier. The rollforward reconciles automatically. The bridge explains itself. The waterfall chart becomes a visualization instead of a monthly spreadsheet project.
At that point, the discussion stops being about the spreadsheet. It becomes about what to do next — and that's when finance teams actually create value.