Deflection Checker Calculator

Check beam deflection against code limits (L/240, L/360, L/480, L/600) using δ = 5wL⁴/(384EI).

Span Length

Uniform Load

kN/m

Elastic Modulus (E)

MPa

Moment of Inertia (I)

mm⁴

Deflection Limit

(1=L/240, 2=L/360, 3=L/480, 4=L/600)

IBC Table 1604.3: roof L/180 (live) to L/240 (total); floor L/240–L/360; sensitive finishes L/480–L/600

Tab to move between fields

Actual Deflection

6.33 mm

Passes Check?

1 (1=yes, 0=no)

Allowable Deflection16.67 mm

Actual / Allowable0.38

How to Use This Calculator

Enter the beam span in feet and the total uniform load in kips per foot.
Input the modulus of elasticity and the moment of inertia for the selected section.
Set the allowable deflection limit (span/240, span/360, span/480) based on the application.
Review the Calculated Deflection in inches and the Deflection-to-Span Ratio.
If the calculated deflection exceeds the limit, increase the section depth or pre-camber the beam.

How the result changes with Span Length

Span Length: Clear span of the beam between supports.
Uniform Load: Total uniformly distributed load on the beam.
Elastic Modulus (E): Modulus of elasticity. Steel = 200,000, concrete ~25,000, wood ~12,000 MPa.
Moment of Inertia (I): Second moment of area of the beam cross-section about the bending axis.
Deflection Limit: Deflection limit per IBC Table 1604.3 and AISC Design Guide 3. 1=L/240 (roof live, or floor without brittle finishes); 2=L/360 (floor supporting plaster/brittle finish, most common); 3=L/480 (ceilings, long-term); 4=L/600 (sensitive equipment/facades).

Identify Input Parameters
4 parameters
Span Length = 6, Uniform Load = 15, Elastic Modulus (E) = 200000, Moment of Inertia (I) = 200000000 = 5 input(s) provided
Calculate Actual Deflection
Actual Deflection
6.33 = 6.33
Calculate Passes Check?
Passes Check?
1 = 1
Calculate Allowable Deflection
Allowable Deflection
16.67 = 16.67
Calculate Actual / Allowable
Actual / Allowable
0.38 = 0.38