Window Thickness Calculator
Calculate minimum window thickness for pressure loading, center deflection, wavefront error, and Fresnel losses.
Optical windows used in vacuum chambers, pressure vessels, and environmental enclosures must withstand mechanical loading without fracture or excessive deflection. Minimum thickness is set by t_min = R√(K · ΔP · SF / M_R), where R is the unsupported radius, K is a support constant (1.1 for simply supported, 0.75 for clamped), ΔP is the pressure differential, SF is the safety factor, and M_R is the material's modulus of rupture. For a chosen actual thickness, the tool also calculates center deflection from the plate bending formula and converts it to approximate wavefront error in waves at 632.8 nm — critical when the window is in a beam path. Uncoated Fresnel reflection losses per surface are computed from the material refractive index. Material presets cover N-BK7, UV fused silica, CaF₂, MgF₂, sapphire, germanium, silicon, ZnSe, ZnS, and BaF₂, with a custom entry for other substrates. Pressure inputs accept atm, psi, kPa, or MPa.