Use this workshop calculation to turn measured dimensions and the selected construction convention into a cut, spacing, fit, or material-planning value.

Deflection limit (m)

Required number input.

Shelf modulus (Pa)

Required number input.

Second moment of area (m⁴)

Required number input.

Uniform load (N/m)

Required number input.

Solve the uniform-load, simply supported elastic-beam formula for maximum span at a specified absolute midspan deflection limit; not a strength check. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Deflection-limited span (m)

The resulting deflection-limited span returned as a number.

• Nominal dimensions, kerf, moisture movement, hardware clearances, wall squareness, and manufacturer instructions can change the required shop dimension. Measure the actual assembly and test critical joints on scrap before cutting finished material.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Complement the calculated dimension with a physical story stick, dry fit, or full-size layout. Follow the hardware, coating, adhesive, or machine manufacturer's limits where they differ from a rule of thumb.

• Shelf Deflection

  Maximum midspan deflection of a simply supported shelf under uniform load, from wL⁴/(EI); assumes small elastic deflection.

• Schlitz Zapfen Masse 1 3 Regel

  One-third-rule tenon thickness and equal shoulder widths from stock thickness; these are starting dimensions, not a strength check.

• Infill Gap Safety Check

  Check whether a railing infill gap keeps the 12 centimeter child-safety limit so a small head cannot pass through.