Units and Conversions¶
Use Edit > Units to choose length (mm, cm, m, in, ft) and force (N, kN, lbf, kip) independently. All 20 combinations also appear in the bottom-right selector; the four original preset names remain unchanged. The dialog previews derived units before applying a change. Apply is undoable; Cancel leaves the project unchanged. These choices persist in 2D/3D projects, recovery snapshots and 3D copies without changing canonical engineering values or invalidating valid results.
For custom choices with mm/cm/m geometry, material stress uses MPa and section properties use mm2/mm4. With in/ft geometry, sections use in2/in4; stress uses kip/in2 for kip forces and psi for other force choices. Moments, distributed loads, weight density and support stiffness use the chosen length/force units. The dialog shows these conventions even for mixed metric/Imperial choices. Files retain their current schema versions and store a deterministic unit key; older application builds that lack the custom choices reject those unit keys.
| Quantity | Imperial (in, kip) | SI (m, kN) | SI (mm, N) | Imperial (ft, kip) |
|---|---|---|---|---|
| Coordinates, lengths, grid, displacements | in | m | mm | ft |
| Forces | kip | kN | N | kip |
| Moments | kip-in | kN-m | N-mm | kip-ft |
| Distributed intensity | kip/in | kN/m | N/mm | kip/ft |
| E and G | kip/in2 | MPa | MPa | kip/in2 |
| Weight density | kip/in3 | kN/m3 | N/mm3 | kip/ft3 |
| Section area | in2 | mm2 | mm2 | in2 |
| Iy, Iz, J | in4 | mm4 | mm4 | in4 |
| Rotation | rad | rad | rad | rad |
Density is weight per volume, not mass density in kg/m3. Load fractions, Poisson ratio, combination factors, and deformation amplification are dimensionless and do not change with units. Switching preserves grid spacing; enter a new value in Edit > Grid when a round metric spacing is wanted. Section and material names are identifiers and are not renamed by conversion.
The model, saved engineering numbers, and solver use canonical inch-kip units. Only input/output boundaries convert. This avoids repeated conversion drift and keeps old projects physically unchanged. Unedited property fields retain their full internal precision even when displayed with fewer decimals. Open diagram windows retain their analyzed geometry and loading, but follow the active unit selection. Unit changes alone do not require another analysis. Conversions use exact inch and pound-force definitions from NIST SP 811, with other factors derived by their physical dimensions.
Source: GUIDE.md. This manual follows the current repository; the published rc1 wheel has a smaller feature set.