Free Tool
Convert Glasses Rx to Contact Lens Power
Your glasses prescription and contact lens power are different. Glasses sit ~12mm from your eye, so a small correction is needed. Enter your spectacle Rx below to find your contact lens equivalent.
Why are they different?
Glasses sit about 12mm in front of your eye (vertex distance). Contact lenses sit directly on the cornea. For prescriptions stronger than ±4.00D this difference changes the effective power — so a direct copy of your glasses Rx will be slightly off.
The formula
CL = SPH ÷ (1 − 0.012 × SPH)
Rounded to nearest 0.25D. CYL and AXIS pass through unchanged.
| SPHERE | CYLINDER | AXIS | ||
| DISTANCE | RE | — | — | |
| LE | — | — | ||
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