Glasses to Contacts Rx Calculator
Convert your glasses prescription to contact lens prescription using vertex distance adjustment for powers above ±4D.
Convert
D
D
mm
Results
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.
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Formula
Adjusted Power = Power / (1 - (vertex × Power))Related Calculators
Vertex Distance Adjustment Calculator
Adjust lens power when changing the vertex distance (e.g., from glasses to contacts or between different frame positions).
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Calculate the total annual cost of wearing contact lenses including lenses, solution, and eye exams.
Visual Acuity Converter
Convert between Snellen fraction, LogMAR, decimal acuity, and MAR notation for visual acuity measurements.
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