Contact Lens Vertex Calculator

Your details

Choose toric if your prescription includes a cylinder power for astigmatism correction.
Spectacle sphere power in diopters. Negative for myopia (short-sight), positive for hyperopia (long-sight).
D
The distance from the back surface of the spectacle lens to the front of the cornea, measured in millimetres. Typically 12-14 mm; use 12 mm if unknown.
mm
Set to 0 for contact lenses (lens rests on the cornea). Set to another value if converting between two different frame vertex distances.
mm
Rounds compensated powers to the nearest 0.25 D manufacturing step. Turn off to see the exact optical value.
Contact lens sphereCompensation applied
-4.75D

Vertex-compensated sphere power for the contact lens

Vertex distance change12mm
Compensation needed?Yes - compensation applied
Spectacle prescription12
Contact lens prescription0

Contact lens sphere (D): -4.75

  • Sphere (after)
  • Vertex change (mm)

Contact lens sphere: -4.75 D (adjusted from -5.00 D spectacle power)

  • Your contact lens sphere (-4.75 D) is stronger (more minus or less plus) than your spectacle sphere (-5.00 D) because a contact lens sits directly on the cornea.
  • Always have a qualified eye care professional confirm the final prescription and perform an over-refraction on the eye - the formula gives the theoretical starting point.

Next stepCompensation is most significant above |4.00 D|: always use the converted value, not the spectacle script, when ordering contact lenses.

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