8.2: Structuring an Engineering Spreadsheet
- Page ID
- 142411
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A disciplined engineering spreadsheet has three clearly separated regions:
| Region | What goes here | Why it matters |
|---|---|---|
| Inputs | Named parameters with values and units | Change once, updates everywhere; auditable |
| Model equations | Formula cells only — no hardcoded numbers | Transparent, checkable by others |
| Outputs / results | Labeled computed values and graphs | Clear interpretation, defensible conclusions |
Every input cell must have a plain-language label, the value, and the unit. The canonical inputs block for the cable tension model:
B3: 9.81 ← Gravity, g (m/s²)
B4: 30 ← Angle, θ (degrees — single-case only)
The model cell references these inputs using absolute references and converts the angle:
Notice: $B$2 locks to the mass cell; RADIANS($B$4) converts degrees to radians before passing to SIN(). Never hardcode a constant inside a formula. Writing =1000*9.81/... hides the input; change the mass and nothing updates.
Figure \(\PageIndex{1}\): Excel single-case cable tension model using labeled inputs, units, absolute cell references, and degree-to-radian conversion. The formula in cell B5 computes the cable tension \(T = mg/(2\sin \theta)\) using mass, gravity, and angle values from the input cells. (Copyright; Jonathan Compton, CC BY-NC 4.0)