Glasses to Contacts Rx Calculator

Convert your glasses prescription to contact lens prescription using vertex distance adjustment for powers above ±4D.

Sphere Power (SPH)

Cylinder Power (CYL)

Vertex Distance

Contact Lens Sphere

-3 D

Contact Lens Cylinder

0 D

Sphere Change

0 D

Cylinder Change

0 D

How to Use This Calculator

Enter your Sphere Power (SPH) from your glasses prescription in diopters (e.g., −3.00 D for myopia).
Enter your Cylinder Power (CYL) if your glasses correct astigmatism; enter 0 if none.
Set the Vertex Distance — the distance from the back of your glasses lens to the cornea, typically 12 mm.
The calculator adjusts sphere and cylinder for the vertex difference only when powers exceed ±4 D.
Review the Contact Lens Sphere and Contact Lens Cylinder outputs — these are the values to give your eye care provider.

How the result changes with Sphere Power (SPH)

Sphere Power (SPH): Sphere power from your glasses prescription in diopters. Negative = myopia, positive = hyperopia.
Cylinder Power (CYL): Cylinder (astigmatism) power from your glasses prescription in diopters. Enter 0 if none.
Vertex Distance: Distance from the back of the glasses lens to the cornea (typically 12 mm).

Adjusted Power = Power / (1 - (vertex × Power))

Identify Input Parameters
Sphere Power (SPH) = -3, Cylinder Power (CYL) = 0, Vertex Distance = 12 = 3 input(s) provided
Calculate Contact Lens Sphere
Contact Lens Sphere
-3 = -3
Calculate Contact Lens Cylinder
Contact Lens Cylinder
0 = 0
Calculate Sphere Change
0 = 0
Calculate Cylinder Change
Cylinder Change
0 = 0