Shelf Span Calculator
Professional shelf span calculator for woodworking and furniture design. Calculate maximum shelf span, load capacity, sag analysis, and support requirements with wood species optimization and safety factors.
⚠️ STRUCTURAL SAFETY NOTICE
Shelf calculations are estimates for typical residential use. For commercial applications, heavy loads, or critical installations, consult a structural engineer. Always use appropriate safety factors and quality materials.
Shelf Specifications
Material Type
Wood Species
Shelf Dimensions
Load Distribution
Shelf Analysis
Enter shelf specifications to calculate load capacity, sag analysis, and support requirements for your shelving project.
Load Capacity
Calculate maximum safe load based on material properties, span, and safety factors. Consider both uniform and point loads.
Sag Analysis
Determine shelf deflection under load. Acceptable sag is typically 1/360 of span for shelving applications.
Wood Species
Different wood species have varying strength properties. Hardwoods generally support more load than softwoods.
Safety Factors
Use appropriate safety factors: 2x minimum, 3x recommended, 4x+ for heavy-duty or commercial applications.
Span Limitations
Maximum span depends on material, thickness, and load. Thicker shelves and stronger materials allow longer spans.
Support Options
Add center supports, edge banding, or increase thickness to extend span capability and reduce sag.
Frequently Asked Questions
A 3/4" plywood shelf can typically span 24-30 inches with moderate loading (20-30 lbs/sq ft). For heavier loads or minimal sag, limit span to 18-24 inches or add center support. Hardwood plywood performs better than softwood plywood.
Acceptable sag for shelving is typically 1/360 of the span (about 1/8" for a 36" shelf). For appearance-critical applications, limit sag to 1/480 of span. Visible sag becomes noticeable at about 1/4" for most people.
Hard maple, oak, and ash are excellent for shelving due to high strength. Cherry and walnut offer good strength with attractive appearance. For painted shelves, poplar is economical. Avoid soft woods like pine for long spans.
Books typically weigh 15-20 lbs per linear foot for paperbacks, 20-25 lbs for hardcovers, and 25-35 lbs for reference books. For planning, use 25-30 lbs per linear foot for mixed book collections on 8-12" deep shelves.
Add center supports when span exceeds material capabilities, when sag is visible, or for heavy loads. Generally, spans over 30" benefit from support. Center supports effectively halve the span for calculation purposes.
Load capacity increases with the cube of thickness. Doubling thickness from 3/4" to 1.5" increases capacity by 8x. However, cost and weight also increase significantly, so optimize thickness for your specific needs.