Shelf Sag Calculator

How It Works

Shelf sag is calculated using the beam deflection formula: d = 5wL^4 / (384EI). The critical factor is thickness — doubling thickness reduces deflection by 8x. Common modulus of elasticity values (psi): Pine 1.2M, Poplar 1.4M, Oak 1.6-1.8M, Maple 1.8M, Plywood 1.5M. A shelf loaded with books carries about 20-25 lbs per linear foot. Span/300 is the standard maximum acceptable deflection.