Assumptions

An assumption is an uncertain input cell. Each simulation iteration, the cell is overwritten with a value sampled from its probability distribution before the workbook recalculates.

Adding an assumption

1. In the sidebar, click + Add under Assumptions.

2. Fill in the fields:

   • Name — a label for this assumption (e.g. "Unit cost")
   • Sheet — select the sheet containing the cell
   • Cell — enter the cell reference (e.g. B4)
   • Distribution — select from the dropdown
   • Parameters — fill in the distribution parameters

3. Click Add. The cell is highlighted in blue in the spreadsheet.

Fields

Field	Description
Name	User-defined label displayed in the sidebar
Sheet	Sheet name (from the IronCalc sheet list)
Cell	Single cell reference (e.g. B4) — assumptions are always single cells
Distribution	Probability distribution for sampling
Parameters	Distribution-specific parameter values

Supported distributions

Distribution	Parameters	Description
constant	value	Always returns the same value — effectively a fixed input
normal	mean, std	Symmetric bell curve
lognormal	mean, sigma	Right-skewed, always positive
uniform	low, high	Any value equally likely in a range
triangular	low, mode, high	Three-point estimate
exponential	rate	Memoryless, right-skewed
gamma	shape, scale	Flexible positive-value distribution
weibull	scale, shape	Wear-out or reliability modeling
poisson	rate	Count-based, integer values

Editing and removing assumptions

• Click the edit icon next to an assumption in the sidebar to change its settings.
• Click the remove icon to delete it. The blue highlight is removed from the spreadsheet.