Estimate max moment, end reaction, and midspan deflection for a simply supported beam under a uniform or midspan point load.
| Max moment (kN·m) | – |
| Reaction (kN) | – |
| Deflection | – |
Use this calculator for a first sketch of a lintel, joist, or header before an engineer sizes the section. Pick uniform load or a point load at midspan, then enter span, load, E, and I.
Uniform: M = wL²/8, each reaction wL/2, deflection 5wL⁴/(384EI). Midspan point: M = PL/4, reactions P/2, deflection PL³/(48EI). Span can be entered in metres (m) or feet (ft). Type load in N/m for uniform, or N for a point load. E is in GPa (steel ~210, C24 timber often ~11). I is in cm⁴ from the section tables. Deflection is shown in millimetres (mm) or inches (in).
Simply supported only. This is not a continuous beam, a cantilever, or a code check of L/360.
Load type: Uniform along the span, or a single point load at midspan.
Span: Clear span, support to support, in m or ft.
Load (N/m or N): N/m if uniform, N if a point load.
E (GPa): Modulus of elasticity in gigapascals.
I (cm⁴): Second moment of area in cm⁴.
Max moment (kN·m): Peak bending moment.
Reaction (kN): Vertical reaction at each support.
Deflection: Midspan sag.
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