# Editing Units

This article explains how to **edit units** for variables and drivers in Model Reef.

You will learn:

* How units affect display and interpretation of values.
* How to change units safely.
* How units interact with bounds and validation.

Units make it clear what a number represents and at what scale.

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### Where to edit units

Units are usually edited in the **Units and bounds panel**, accessible from:

* The Variable Editor.
* The Driver Editor for certain drivers that behave like assumptions.

Units apply to the variable or driver whose editor you have open.
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### Types of units

Two main aspects of units are:

* **Nature of the quantity**, for example:
  * Currency.
  * Physical units (items, hours, kilograms).
  * Percentages.
* **Display scale**, for example:
  * Whole units.
  * Thousands.
  * Millions.

The nature of the quantity helps humans interpret the value. The display scale affects how numbers are shown on screen, not how they are stored.
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### Changing display scale

If a variable is stored in whole currency units, you can switch the display to thousands or millions.

When you change display scale:

* Underlying stored values do not change.
* Only the way they are shown in grids, charts and reports changes.
* This can be done per variable or per output context depending on the interface.

For example, `1,000,000` stored units may show as `1.0` if the display scale is millions.
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### Consistency across the model

To keep the model readable:

* Use the same unit conventions for similar variables, such as all revenue lines in the same currency and scale.
* Avoid mixing units for comparable items, as it makes comparisons harder.
* Use notes to document any variable that uses unusual units.

Consistent units also make charts and dashboards more intuitive.
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### Units and formulas

When using variables and drivers in formulas:

* Be aware of the underlying units being combined.
* Ensure that multiplications and divisions are conceptually correct (for example price times quantity, not price times price).
* If necessary, convert units before using a series in a formula.

Model Reef does not automatically enforce dimensional analysis; that judgement remains with the modeller.
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### Units and validation

Units interact with validation in two ways:

* Bounds are defined in the same scale as the stored values.
* Display units must be understood when interpreting error or warning messages.

If a variable is displayed in thousands, a bound that seems large in the interface may still be appropriate at the underlying scale.
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## Related articles

* [Editing Bounds](/syntax/how-input-fields-work/editing-bounds.md)
* [Editing Driver Time Series](/syntax/drivers-syntax/editing-driver-time-series.md)
* [Mapping Units & Frequency](/help/importing-and-data-inputs/mapping-units-and-frequency.md)
* [Build a Debt Schedule & Covenants Model](/how-tos/investment-and-transactions/build-a-debt-schedule-and-covenants-model.md)


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