Reference
MASSPROP in AutoCAD
How AutoCAD's MASSPROP reports the mass properties of 3D solids and regions: volume, area, centroid, moments of inertia, and the .mpr file. Try it free online.
MASSPROP measures 3D solids and regions. Select them and press Enter: the report is written at the command prompt, in AutoCAD's columns, then it asks whether to write it to a file. A set with neither says No solids or regions selected., and ends.
For solids, the set is measured as one body with a density of 1, so the mass is the volume: mass, volume, bounding box, centroid, moments of inertia, products of inertia and radii of gyration, all about the current UCS, then the principal moments about the centroid with their directions. Solids that overlap are counted twice. For regions in the UCS's XY plane: area, perimeter, bounding box, centroid, moments and product of inertia, radii of gyration and principal moments; a region off that plane gives its area, perimeter, bounding box and centroid alone. Regions come first, then solids; regions outside the plane of the first are left out and counted. Numbers are written at the drawing's precision, set with UNITS, and they are exact, the solids' integrated face by face. MASSPROP changes nothing in the drawing; it is typed, as in AutoCAD, whose ribbon has no button for it.
- Command:
MASSPROP - Panel: Inquiry & view
- Try it: Open the editor, type
MASSPROPand press Enter.
At the command line
The engine draws it and writes its history as you would type it: the prompts in AutoCAD 2027's order, with the same option letters.
- Command: MASSPROP
- Select objects: 1 found
- Select objects:
- ---------------- SOLIDS ---------------- Mass: 60000.00 Volume: 60000.00 Bounding box: X: 0.00 -- 60.00 Y: 0.00 -- 40.00 Z: 0.00 -- 25.00 Centroid: X: 30.00 Y: 20.00 Z: 12.50 Moments of inertia: X: 44500000.00 Y: 84500000.00 Z: 104000000.00 Products of inertia: XY: -36000000.00 YZ: -15000000.00 ZX: -22500000.00 Radii of gyration: X: 27.23 Y: 37.53 Z: 41.63 Principal moments and X-Y-Z directions about centroid: I: 11125000.00 along [1.00 0.00 0.00] J: 21125000.00 along [0.00 1.00 0.00] K: 26000000.00 along [0.00 0.00 1.00]
- Write analysis to a file? [Yes/No] <N>:
Options
Yes (Y)
At the file question, whose default is No: writes the report to a file, as AutoCAD writes it, line for line. In AutoCAD a dialog asks where; in a browser the download is that dialog, and the file is named after the drawing, .mpr.
What it does not do yet
Units after each number with architectural or engineering units (sq in, cu in, lb), which AutoCAD writes: here no unit follows a number. Choosing the file's name, and the question before replacing one. Far from the origin, AutoCAD writes large numbers in exponent form and loses digits, and its last digit can differ by its own rounding: MellowCAD's are exact. For a solid with two equal principal moments, the pair of directions AutoCAD's rounding picks.
What it does and still lacks, in detail (in English)
Questions
How do I find the volume of a 3D solid in AutoCAD?
Run MASSPROP, pick the solid and press Enter: Volume is the report's second line. The session's box of 60 by 40 by 25 gives 60000. Press Enter at the file question to end.
How do I find the centroid of a shape?
Make it a region with REGION, or a solid, then run MASSPROP and pick it: Centroid gives its X and Y, and Z for a solid, in the current UCS.
Why does MASSPROP say no solids or regions selected?
What you picked is neither: lines, polylines, circles and hatches have no mass properties, and a block holding a solid is not a solid. Turn closed shapes into regions with REGION, or into solids with EXTRUDE.
Why is the mass equal to the volume?
MASSPROP measures with a density of 1, as AutoCAD does: solids have no material here. Multiply the volume by the material's density for its real mass.