This article focuses on drivers in driver tables. Drivers can also be used in databases, which have additional behavior covered in Formulas in databases.
What is a driver?
A driver in Runway is a structured chunk of time series data. It has a human-readable name and represents values that shape your business model, such as revenue, expenses, headcount, renewal dates, or department attributes. Drivers act as the primary elements in tables and formulas. Conceptually, a driver is similar to:- A row in an Excel model
- A variable in other modeling systems
Why use drivers?
Drivers offer several advantages over traditional spreadsheet modeling:- Portable: Drivers can be referenced in formulas, added to tables, and visualized in charts without dealing with cell ranges. They stay synced across your model.
- Time-native: Every business assumption changes over time. Drivers make it easy to project those changes across months.
- Dimensional: Drivers can use dimensions to structure your model as complexity grows.
Driver formulas
Drivers contain formulas that define their values across different time periods.- Forecast formula: Calculates projected values for future periods after the last close.
- Actuals formula: Defines historical values through the last close.
Formula inheritance
Runway applies smart defaults to fill in missing formulas when needed. The inheritance hierarchy determines how formulas are applied. Actuals formula inheritance hierarchy:| Priority | Rule |
|---|---|
| First | Explicitly set actuals formula for the driver. |
| Next | Default actuals formula set for the database column the driver belongs to. |
| Fallback | Driver’s forecast formula, if no actuals formula is set. |
| Priority | Rule |
|---|---|
| First | Explicitly set forecast formula for the driver. |
| Next | Default forecast formula set for the database column the driver belongs to. |
| Fallback | Global default formula: the driver’s own value from last month (shown in the editor as the driver’s name with the Last month time period). |
Overriding formula values
Hardcoding a cell value overrides the formula for that period. Overridden cells are visually marked so you can distinguish them from formula-driven values. You can also tag overrides to a plan to keep the business context attached to the change. Learn more in Plans.Drill-ins
When you need to understand why a driver has a value, use drill-ins to expand the driver row and inspect the inputs that feed its formula.Driver types
Drivers store time series data in one of three user-facing formats:- Number: Quantitative values like revenue, expenses, or headcount.
- Date: Time-based values like project start dates or contract renewals.
- Dimension: Categorical values from dimensions, often used when working with HRIS data or other segmented sources.
When entering explicit dates in formulas, use the format
YYYY-MM-DD enclosed in single quotes.
- Driver formulas must output values that match the driver’s type.
- Date functions that return dates require Date drivers.