Blue Butterfly | Docs — Formula Columns

A formula column computes its value automatically from other columns in the same row. The cell is read-only in the spreadsheet — its value updates whenever a referenced column changes. Useful for derived quantities like interval thickness, unit conversions, RQD, or any value you’d otherwise type a formula for in Excel.

Create a formula column

In Templates → Data Tables, add a column and set its Type to formula. A Formula field appears on the column card. Enter a mathjs expression and save.

The same applies to drillhole template fields — set type to formula and provide an expression.

Expression syntax

Formulas use mathjs — the same expression engine as the validation custom rule. Within an expression, reference any other column in the same row by its name.

Examples

Formula	Result
`depth_to - depth_from`	Interval thickness
`(au_g_t * specific_gravity) / 31.1035`	Au g/t to oz/t conversion
`core_recovery / (depth_to - depth_from) * 100`	Recovery percentage
`(rqd_length / drilled_length) * 100`	RQD percentage
`depth_from + (depth_to - depth_from) / 2`	Midpoint depth
`cu_pct * tonnes_per_m * (depth_to - depth_from)`	Contained metal

Any valid mathjs expression is supported — arithmetic, comparison, logical, conditional (x > 0 ? x : 0), trigonometric, etc.

Behaviour in the spreadsheet

Purple type badge in the templates editor identifies formula columns.
Greyed out cells in the spreadsheet — you cannot click into them to type.
Auto-recalculation. Whenever you edit a referenced column, the formula re-evaluates and the cell updates immediately.
Empty inputs. If a referenced column is blank, the formula cell is also blank (the formula doesn’t run on partial input).
Errors. If the expression fails (divide by zero, undefined column, syntax error), the cell shows ERROR. Fix the expression in Templates and the cell recalculates.

Tips

Reference exact column names. Names are case-sensitive. If your column is depth_from, the formula must use depth_from — not Depth From or depthFrom.
Use formula columns for derived values, not for one-time calculations. If you only need a value once, calculate it in Excel before importing. Formula columns shine when the underlying data changes.
Combine with validation. Run a custom validation rule against the formula’s output too — e.g., interval_m > 0 && interval_m < 100.
No side effects. Formulas are pure functions of other columns in the same row. They cannot reference other rows, other tables, or the drillhole’s collar fields.