All Calculators
Lens Cutout Calculator
Check if a lens will cut out before you order
Frame Measurements
Patient Measurements
Prescription (optional)
Lens Blank
Key Formulas
Frame PD (GCD)
Frame PD = A + DBL
The distance between the geometric centers of the lens openings.
Decentration
Dec/lens = (Frame PD - Patient PD) / 2
Positive = decenter nasal (in). Negative = decenter temporal (out).
Effective Diameter (ED)
ED ≈ √(A² + B²)
The longest diagonal of the frame shape. Use manufacturer's ED if available.
Minimum Blank Size
MBS = ED + 2|Dec| + Safety
Safety margin is typically 2-4mm for edging tolerance.
Frequently Asked Questions
A lens "cuts out" when the uncut lens blank isn't large enough to completely fill the frame after cutting. This happens when the frame is too large, the patient's PD differs significantly from the frame's geometric center, or when high-wrap frames require extra material. The lens literally has a piece missing at the edge.
