Free lens thickness calculator: spherical sagitta from diameter and radius of curvature in mm, edge thickness, plano-convex or symmetric biconvex model, center thickness, charts, scenario rows—STEM education, not Rx lab software.
Important: This is a geometry classroom model for ideal spherical caps—not a spectacle Rx tool, not a contact-lens fitter, and not a substitute for CAD from your lab or manufacturer. Real lenses add aspheric terms, bevels, centering error, and mounting loads.
Summary: Enter a clear diameter (mm), a convex surface radius of curvature R (mm), a minimum edge thickness, and whether one or both sides use that sagitta. The tool computes sag and center thickness, shows quick charts, and prints scenario rows—same stress-test spirit as other calculators here.
Lens thickness calculator (spherical sagitta)
For a circular clear aperture of radius y = diameter⁄2, a spherical surface bulge height is sag = R − √(R² − y²) when |y| < R and the surface is convex toward the outside of that radius.
Geometry (short)
Plano–convex (one powered side): center thickness ≈ edge thickness + one sag.
Symmetric biconvex (same |R| both sides, model as two identical sags): center thickness ≈ edge thickness + 2 × sag.
If y ≥ R, the sphere cannot span the chord—inputs are physically inconsistent for this idealization.
