AISC M-Shapes: Dimensions and Section Properties
Browse AISC miscellaneous M-shapes by depth and weight. Compare dimensions and section properties in imperial or metric units.
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Showing AISC · M-Shapes · Imperial
AISC Shapes Database v16.0 · 2,299 sections
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Showing the most relevant 75 sections.
| Designation | Weight (lb/ft) | Depth, d (in) | Flange width, bf (in) | Area (in²) | Ix (in⁴) | Sx (in³) |
|---|---|---|---|---|---|---|
| M12.5x11.6 | 11.6 | 12.5 | 3.5 | 3.4 | 80.3 | 12.8 |
| M12.5x12.4 | 12.4 | 12.5 | 3.75 | 3.63 | 89.3 | 14.2 |
| M12x10 | 10 | 12 | 3.25 | 2.95 | 61.7 | 10.3 |
| M12x10.8 | 10.8 | 12 | 3.07 | 3.18 | 66.7 | 11.1 |
| M12x11.8 | 11.8 | 12 | 3.07 | 3.47 | 72.2 | 12 |
| M10x9 | 9 | 10 | 2.69 | 2.65 | 39 | 7.79 |
| M10x7.5 | 7.5 | 9.99 | 2.69 | 2.22 | 33 | 6.6 |
| M10x8 | 8 | 9.95 | 2.69 | 2.37 | 34.6 | 6.95 |
| M8x6.2 | 6.2 | 8 | 2.28 | 1.82 | 17.6 | 4.39 |
| M8x6.5 | 6.5 | 8 | 2.28 | 1.92 | 18.5 | 4.63 |
| M6x4.4 | 4.4 | 6 | 1.84 | 1.29 | 7.23 | 2.41 |
| M6x3.7 | 3.7 | 5.92 | 2 | 1.09 | 5.96 | 2.01 |
| M5x18.9 | 18.9 | 5 | 5 | 5.56 | 24.2 | 9.67 |
| M4x4.08 | 4.08 | 4 | 2.25 | 1.27 | 3.53 | 1.77 |
| M4x6 | 6 | 3.8 | 3.8 | 1.75 | 4.72 | 2.48 |
| M3x2.9 | 2.9 | 3 | 2.25 | 0.914 | 1.5 | 1 |
Family overview
What are AISC M-Shapes?
AISC M-shapes are miscellaneous I-sections whose proportions fall outside the standard W and S series. They share the depth × weight designation pattern and can be useful when a lighter or differently proportioned rolled I-section is needed. Strong and weak axes follow the usual open-section conventions. Use tabulated geometry rather than the rounded designation numbers for detailing. This hub filters the finder to M-shapes so you can compare nearby sizes, open a designation page or analyze a section in Optimal Beam.
Designations
Understanding M-Shapes designations
M12×10.8
M designations follow the same nominal depth × weight pattern as W-shapes. For example M12×10.8 indicates an approximate 12 in nominal depth and about 10.8 lb/ft.
Properties
M-Shapes properties explained
These properties are especially relevant when comparing M-Shapes. View the complete property glossary.
| Symbol | Property | Units | Why it matters |
|---|---|---|---|
| Weight | Weight | lb/ft, kg/m | Mass per unit length; used for self-weight and economy comparisons |
| d | Overall depth | in, mm | Overall depth and clearance |
| bf | Flange width | in, mm | Overall flange width and lateral behaviour |
| tw | Web thickness | in, mm | Web thickness and shear-related behaviour |
| tf | Flange thickness | in, mm | Flange thickness and flexural/local behaviour |
| A | Cross-sectional area | in², mm² | Total steel cross-sectional area |
| Ix | Moment of inertia (x) | in⁴, mm⁴ | Major-axis flexural stiffness |
| Iy | Moment of inertia (y) | in⁴, mm⁴ | Minor-axis flexural stiffness |
| Sx | Elastic section modulus (x) | in³, mm³ | Elastic bending property about the x-axis |
| Sy | Elastic section modulus (y) | in³, mm³ | Elastic bending property about the y-axis |
| Zx | Plastic section modulus (x) | in³, mm³ | Plastic bending property about the x-axis |
| Zy | Plastic section modulus (y) | in³, mm³ | Plastic bending property about the y-axis |
| rx | Radius of gyration (x) | in, mm | Strong-axis radius of gyration |
| ry | Radius of gyration (y) | in, mm | Weak-axis radius of gyration and lateral stability relevance |
| J | Torsional constant | in⁴, mm⁴ | Torsional constant |
| Cw | Warping constant | in⁶, mm⁶ | Warping constant for lateral-torsional behaviour |
Library summary
Computed M-Shapes summary
The current AISC M-Shapes library contains 16 sections across 8 nominal-depth series. Published weights range from 2.90 to 18.90 lb/ft , and actual depths range from 3.00 to 12.50 inches .
- Lightest section
- M3X2.9
- Heaviest section
- M5X18.9
- Ix range
- 1.50 – 89.30 in⁴
- Sx range
- 1.00 – 14.20 in³
Selection
How to compare M-Shapes
- Confirm that an M-shape is specified or acceptable for the project.
- Compare depth, weight and Ix against nearby W or S alternatives.
- Check flange and web thickness for local behaviour and connections.
- Analyze candidates under the same span and loads before selecting.
Beam calculator
Analyze this family in Optimal Beam
Select any M-shape and load it into the Optimal Beam calculator.
Source: AISC Shapes Database v16.0 · Verified July 2026 · View methodology
Questions & answers
M-Shapes FAQs
What is an AISC M-shape?
An M-shape is a miscellaneous I-section that does not fall into the W or S series. It uses the same depth × weight designation style as W-shapes.
When would I use an M-shape instead of a W-shape?
When project constraints or availability favour a miscellaneous proportion, or when a tabulated M-shape matches the required depth and weight better than nearby W sizes. Always verify properties and supply.
Do M-shapes use the same axis conventions as W-shapes?
Yes. The x-axis is the strong axis and the y-axis is the weak axis for typical open I-sections.
Can I analyze an M-shape in Optimal Beam?
Yes. Select the section and choose Analyze to load its properties into the beam calculator.