Shelf Load & Deflection Estimator
Compare how span, thickness, depth and loading affect the initial sag of an end-supported shelf.
Set up your calculation
An illustrative example is loaded. Replace its values with your measurements, costs or documented settings.
Calculation
Your result
- Estimated initial sag
- 0.06 in
- Chosen sag reference
- 0.2 in
- Load at that deflection only
- 166.667 lb
- Reference comparison
- Within chosen sag reference
Increasing thickness reduces sag with the cube of thickness. A center support can be much more effective than a small thickness increase.
The quote handoff carries your inputs and assumptions. Only an explicit base cost is suggested as a quote cost; prices, rates and measurements remain planning notes.
How it works
I = depth × thickness³ ÷ 12. Uniform total load W: sag = 5WL³ ÷ (384EI). Center point load: sag = WL³ ÷ (48EI). Dimensions are inches, E is psi, and loads are pounds-force.
- Simply supported at both ends, constant rectangular section, small elastic deflection. Enter a modulus appropriate to the actual grade and panel orientation; the example is illustrative.
- The sag reference is a comparison target, not a structural capacity. Shelf weight belongs in the load. Creep, bending strength, brackets, fasteners and joint failure are not evaluated.
Learn the method in the Academy
Follow the matching lesson or workshop reference before applying the result.
Use this in your project
Continue with the next measurement or cost, then keep the assumptions with your quote.
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