Overview · What & why
A decision, before a calculation.
Reliable models use consistent units and transparent formulas. Annual rent per square foot is different from total monthly rent; an occupancy percentage is a fraction, not a whole number. A spreadsheet reference links a formula to an input. Relative references move when copied; absolute references keep a selected row or column fixed. The same discipline matters in browser models.
A concrete example
100,000 SF × $10/SF/year × 0.95 gives $950,000/year. Using 95 instead of 0.95 gives $95M, a unit error of 100 times. Dividing annual revenue by 12 gives a monthly average, not a lease-up forecast.
What to remember
Units and references are part of the model, not cosmetic annotations.
Before using this in a project: A unit legend, formula map and at least one independently calculated control total.