Calculators

BAC / Thickness

Surface powers, sag, centre & edge thickness

Lens powerDBase (front) curveDRefractive indexLens diametermm

Minimum edge thicknessmm

Enter values to calculate

Reference

Lensmaker: F₁ = (n − 1)/r₁, F₂ = (1 − n)/r₂. Sag s = r − √(r² − y²).

Vogel's rule for base curve: plus lenses ≈ SE/2 + 6; minus lenses ≈ SE/6 + 6. Min thickness: ~2.0 mm CR-39 minus, ~1.0–1.5 mm polycarbonate/high-index.

Index: CR-39 1.498 · Trivex 1.53 · Polycarbonate 1.586 · 1.67 · 1.74.