Free eye check · 1 min · No sign-up
Glasses to contact lens prescription converter
See how your glasses prescription translates to contact lens power using vertex distance, including toric lenses for astigmatism.
Loading the check…
A screening aid, not a diagnosis. Screens, lighting and distance affect results. If something looks wrong, or your vision changes suddenly, see an eye-care professional. Medical disclaimer
The vertex distance formula
A lens has a different effect depending on how far it sits from the eye. The converter uses the standard formula Fc = F / (1 − d × F), where F is the glasses power and d is the vertex distance in metres. For minus lenses, the contact lens power is weaker than the glasses; for plus lenses it is stronger.
For astigmatism, each main direction (meridian) is converted separately, then turned back into sphere and cylinder. For small amounts of astigmatism, a spherical lens using the spherical equivalent often works well.
Why you still need a fitting
Contact lenses rest on the cornea, so their curve and size must match your eye. A poorly fitting lens can cut off oxygen to the cornea, scratch it or move around and blur vision. Contact lens wearers also have a higher risk of serious eye infections, so follow the contact lens safety guide.
Questions people ask
Why is my contact prescription different from my glasses?
Glasses sit about 12 mm in front of the eye while contacts sit on it. Above about 4 diopters this distance changes the power needed. Contacts also need a base curve and diameter from a fitting.
Can I order contacts with my glasses prescription?
No. In the US, contact lens sellers must verify a contact lens prescription, which requires a fitting.