Sizu Home › Calculators › Shelf Deflection
Enter a load, span, shelf width and thickness, then press Calculate.
From the book — Chapter 8. Deflection = 5WL³ ÷ (384EI), I = width × thickness³ ÷ 12, E ≈ 1.2 million psi for plywood. A shelf passes if the sag is under span ÷ 360.
A doubled span sags 8× as much; doubled thickness cuts sag to 1/8. Everything stays in your browser — no sign-up, nothing stored.