Units & Bounds
This article explains how units and bounds work in Model Reef and how they help you keep variables well behaved and easy to interpret.
You will learn:
What units are and why they matter.
How bounds prevent unrealistic or broken assumptions.
Where to see and edit units and bounds.
Good practice for setting units and bounds across a model.
What units are
Each variable and driver in Model Reef has units, for example:
Currency: GBP, USD, EUR, AUD.
Counts: units, customers, orders, FTEs, hours.
Rates: percent, basis points, index values.
Units are used for:
Display formatting in tables, charts and dashboards.
Tool tips and labels in the UI.
Helping humans interpret what a series represents.
The model calculations treat values as numeric but units make that numeric content meaningful.
What bounds are
Bounds define sensible minimum and maximum values for a variable or driver, for example:
Revenue cannot be negative below a certain threshold in a given scenario.
Volumes cannot go below zero.
Discount rates should stay within a realistic range.
Growth rates should not exceed a hard cap without explicit decision.
Bounds do not replace judgement, but they help catch typos and extreme inputs.
Bounds are safeguards to catch unrealistic or extreme inputs — they are not a substitute for modelling judgement.
How units and bounds are used in the UI
In the variable or driver editor you can:
Set or change units from a defined list or by entering custom units.
Set lower and upper bounds for values.
See warnings or validation messages if values fall outside the bounds.
In dashboards and charts:
Units influence axis labels, legends and KPI card formatting.
Bounds can help you notice unusual behaviour when a series suddenly hits a cap or floor.
These features improve readability and reduce modelling errors.
Good practice for units
Guidelines:
Use the model currency for all monetary variables by default.
Use counts for volumes and headcount, not implicit currency.
Use percent or index units for growth, margins and modifiers.
Keep units consistent across similar drivers and variables, especially when combining them in formulas.
Clear units make cross checking much easier for reviewers and collaborators.
Good practice for bounds
Guidelines:
Set bounds narrowly for sensitive or critical assumptions to catch out of range inputs.
Use wider bounds for series where volatility is expected, but still prevent impossible states such as negative headcount.
Document in notes where bounds represent a hard constraint rather than just a warning.
Review bounds when shifting to new scenarios or business environments.
Bounds are especially helpful when junior modellers or non finance users are editing assumptions.
Related articles
Last updated