How to use the simply supported beam midspan deflection calculator
Find how far a beam sags at its centre under a central point load. Enter centre load, span, elastic modulus, second moment of area in the fields above; the midspan deflection are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “beam sag at centre”, “midspan deflection”, “floor joist bending”, “calculate simply supported beam midspan deflection”, “find midspan deflection”.
Formula
Variables
- P — Centre load (N)
- Lb — Span (m)
- E — Elastic modulus (Pa)
- I — Second moment of area (m⁴)
Worked example
With centre load = 5000 N, span = 4 m, elastic modulus = 200000000000 Pa, second moment of area = 0.00012 m⁴, the calculator gives midspan deflection ≈ 0.00027778 m; midspan deflection ≈ 0.2777778 mm.
Frequently asked questions
What is the simply supported beam midspan deflection calculator used for?
Find how far a beam sags at its centre under a central point load. It helps with questions such as “beam sag at centre”, “midspan deflection”, “floor joist bending”.
What is the formula for the simply supported beam midspan deflection calculation?
Midspan deflection (m) = P × Lb^3 / (48 × E × I). Midspan deflection (mm) = [Midspan deflection] × 1000. Here P is centre load (N), Lb is span (m), E is elastic modulus (Pa), I is second moment of area (m⁴).
What inputs do I need for the simply supported beam midspan deflection calculator?
You need centre load in N, span in m, elastic modulus in Pa, second moment of area in m⁴. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the simply supported beam midspan deflection calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the simply supported beam midspan deflection result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.