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Structural · W — wide-flange

W8x31 Steel Beam — Dimensions & Properties

W8x31 weighs 31 lb/ft and is about 8 in deep. Below: the full AISC section properties, a scaled cross-section, and a pre-filled weight calculator.

Weight
31lb/ft
Depth
8in
Width
7.995in
Area
9.13in²
Shape
W8X31 · W — wide-flange

Enter feet + inches, e.g. 20' or 18' 6".

= 20' (240″)
pcs
Cost estimate (optional)
$/lb

Optional. Prices are volatile — use your current mill/supplier rate.

Total weight
1 × W8X31
620lb
Per piece
620lb
Pieces
1
Total
620lb
Tons
0.31t
d8"bf 7.995"tw 0.285
ƒShow the math
  1. 1.Weight per foot (from AISC)per AISC Shapes Database v16.0

    W8X31 is a listed shape; its nominal weight is a published property.

    = 31 lb/ft
  2. 2.Length in feet
    length (in) ÷ 12
    240 ÷ 12
    = 20 ft
  3. 3.Weight per piece
    weight per foot × length
    31 × 20
    = 620 lb
  4. 4.Total weight
    weight per piece × quantity
    620 × 1
    = 620 lb
  5. 5.Convert to tons
    total lb ÷ 2000
    620 ÷ 2000
    = 0.31 tons

Section properties

Geometry
Weight
31lb/ft
Area, A
9.13in²
Depth, d
8in
Flange width, bf
7.995in
Flange thick, tf
0.435in
Web thick, tw
0.285in
Strong axis (x-x)
Ix
110in⁴
Sx
27.5in³
Zx
30.4in³
rx
3.47in
Weak axis (y-y)
Iy
37.1in⁴
Sy
9.27in³
Zy
14.1in³
ry
2.02in
Torsion & warping
J
0.536in⁴
Cw
530in⁶
Before you rely on this
  • Listed weight is the AISC theoretical (nominal) weight per foot. Actual mill weight varies within ASTM rolling tolerance, roughly ±2.5%.
  • This is bare member steel only. Add plates, stiffeners, connections, bolts, and coatings for a full erected-steel takeoff.

Similar shapes

Same series and nearest depths — compare weight and section modulus when you are sizing.

W8x10 10 lb/ftW8x13 13 lb/ftW8x18 18 lb/ftW8x24 24 lb/ftW8x40 40 lb/ftW8x48 48 lb/ftW8x67 67 lb/ftW10x33 33 lb/ftW10x12 12 lb/ftW10x49 49 lb/ft

W8x31 — questions

How much does a W8x31 weigh per foot?
A W8x31 weighs 31 lb/ft. Over a 20-foot length that is 620 lb (0.31 tons); a 30-foot length is 930 lb.
What are the dimensions of a W8x31?
W8x31 has an actual depth of 8 in and a flange width of 7.995 in, a flange thickness of 0.435 in, and a web thickness of 0.285 in. Cross-sectional area is 9.13 in².
What is the moment of inertia and section modulus of a W8x31?
About its strong axis, W8x31 has a moment of inertia Ix of 110 in⁴ and a section modulus Sx of 27.5 in³, with a plastic section modulus Zx of 30.4 in³. Use these with your engineer's design values — they are geometric properties, not an allowable load.
What does W8x31 mean?
The W means wide-flange. The first number is the nominal depth in inches and the second is the weight in pounds per foot — so W8x31 is a nominally 8-inch-deep wide-flange beam weighing 31 lb/ft (actual depth 8 in).

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Sources & references

Estimates for planning purposes only. Verify all results against the code edition adopted in your jurisdiction and with your Authority Having Jurisdiction (AHJ). This tool is not a substitute for a licensed professional engineer. See our methodology, sources, and code editions.

Data: AISC Shapes Database v16.0, © AISC — used per its developer-use provision.