Glass Thickness Load Calculator
Calculate the minimum glass thickness required to withstand a specified uniform load (wind pressure) based on pane dimensions, support conditions, and glass type using the glass stress formula per ASTM E1300.
Uniform lateral load (wind pressure). Typical: 500–3000 Pa
Typical: 2.5 for wind load per ASTM E1300
Enter pane dimensions, load, and conditions above, then click Calculate.
Formulas Used
Maximum bending stress in a rectangular glass plate (Roark's Formulas for Stress and Strain, Table 11.4):
σmax = β · q · a² / t²
Where:
- σmax — maximum bending stress (Pa)
- β — dimensionless stress coefficient (function of aspect ratio b/a and support condition, from Roark Table 11.4)
- q — uniform lateral load / wind pressure (Pa)
- a — short side of pane (m)
- t — glass thickness (m)
Required thickness:
treq = a · √(β · q / σallow)
Design allowable stress:
σallow = σglass / SF
Maximum deflection (four-sided simply supported):
δmax = α · q · a⁴ / (E · t³)
Where α is the deflection coefficient from Roark Table 11.4, E = 70 GPa (glass modulus of elasticity).
Serviceability deflection limit (ASTM E1300):
δlimit = a / 60
Assumptions & References
- Glass is modelled as a thin elastic plate with uniform lateral (wind) pressure.
- Stress coefficients (β) and deflection coefficients (α) are taken from Roark's Formulas for Stress and Strain, 8th Ed., Table 11.4 for rectangular plates with simply supported edges.
- Three-sided support uses a conservative factor of 1.33× applied to the four-sided β value.
- Two-sided (one-way) support is treated as a simply supported beam strip spanning the short direction.
- Allowable stress values per ASTM E1300 – Standard Practice for Determining Load Resistance of Glass in Buildings: Annealed 23.3 MPa, Heat-Strengthened 46.6 MPa, Fully Tempered 93.1 MPa.
- Default safety factor of 2.5 is consistent with ASTM E1300 for wind load applications.
- Standard glass thicknesses (3, 4, 5, 6, 8, 10, 12, 15, 19, 22, 25 mm) per ASTM C1036 and EN 572.
- Modulus of elasticity for glass: E = 70 GPa; Poisson's ratio: ν = 0.22.
- Deflection serviceability limit: a/60 per ASTM E1300 Section 5.
- This calculator applies to monolithic glass only. Laminated, insulated, or wired glass requires additional analysis.
- Results are indicative only. Final glass specification must be confirmed by a qualified structural or façade engineer.