Beam Load Capacity Calculator
Maximum allowable UDL on a simply supported beam — strength and deflection checks.
INPUTS
m
×10³ mm³
×10⁶ mm⁴
GPa
MPa
RESULTS
Allowable moment M = σ·S
91.9 kN·m
Max UDL by strength (8M/L²)
20.42 kN/m
Max UDL by deflection (L/360)
16.51 kN/m
Governing allowable UDL
16.51 kN/m
Total load capacity W = wL
99.1 kN
Governing criterion
Deflection (span/360)
How it works
A beam must pass two independent checks: stress (M = wL²/8 ≤ σallow·S) and stiffness (δ = 5wL⁴/384EI ≤ span/limit). Strength capacity falls with L², deflection capacity with L³ — so short spans are strength-governed and long spans deflection-governed. The crossover is why 'how much can this beam hold' always needs both answers.
Worked example
IPE 300 (S = 557×10³ mm³, I = 83.6×10⁶ mm⁴) on a 6 m span at 165 MPa allowable: strength gives w = 8·91.9/36 = 20.4 kN/m, but span/360 deflection allows only 16.5 kN/m — deflection governs, as is typical for longer steel spans.
Frequently asked questions
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