Steel Beam Selection Calculator

Determine required section modulus, moment of inertia, and approximate beam weight for steel beam design with uniform and point loads.

Inputs

Span Length

Uniform Load

kN/m

Point Load at Midspan

Deflection Limit (L/...)

AISC/IBC: floor live load L/360; floor total load L/240; roof L/180; long-term L/480

Steel Yield Strength (Fy)

MPa

ASTM: A992 W-shapes Fy=345 MPa; A36 plates Fy=250 MPa; A572 Gr.50 Fy=345 MPa

Tab to move between fields

Results

Required Moment Capacity

165 kN·m

Required Section Modulus

724,638 mm³

Required Moment of Inertia168,750,000 mm⁴

Max Deflection (at req. I)16.67 mm

Est. Weight per Foot2,463.77 lb/ft

How to Use This Calculator

Enter the beam span in feet and the tributary width in feet.
Input the dead load and live load in psf, including any point loads.
Set the allowable deflection limit (span/240 or span/360) and the steel yield strength.
Review the Required Plastic Section Modulus (Zx) and the Recommended Wide-Flange Section.
Verify the selected section against shear capacity and deflection limits before finalizing.

How the result changes with Span Length

Span Length	Required Moment Capacity	Required Section Modulus
3.45	72.88 kN·m	320,076 mm³
11	440 kN·m	1,932,367 mm³
20	1,250 kN·m	5,489,679 mm³
27	2,160 kN·m	9,486,166 mm³

What each input means

Span Length: Clear span length of the beam between supports.
Uniform Load: Distributed load along the entire beam length in kN per meter.
Point Load at Midspan: Concentrated load applied at the center of the beam span.
Deflection Limit (L/...): Deflection limit divisor per AISC 360 Design Guide and IBC. L/360 for floors with plaster ceilings; L/240 for floors without brittle finishes; L/180 for roofs with no ceiling. AISC Design Guide 3 recommends L/360 for walking vibration.
Steel Yield Strength (Fy): Yield strength of the steel per ASTM standard. ASTM A992 (W-shapes, Grade 50): Fy=345 MPa (standard for wide-flange); ASTM A36: Fy=250 MPa (plates, angles); ASTM A572 Gr. 50: Fy=345 MPa; A588 weathering: Fy=345 MPa.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Span Length = 6, Uniform Load = 20, Point Load at Midspan = 50, Deflection Limit (L/...) = 360 = 5 input(s) provided
Calculate Required Moment Capacity
Required Moment Capacity
165 = 165
Calculate Required Section Modulus
Required Section Modulus
724638 = 724638
Calculate Required Moment of Inertia
Required Moment of Inertia
168750000 = 168750000
Calculate Max Deflection
Max Deflection
16.67 = 16.67

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