Terms of Service

Last updated: September 2026

Using this site

Contact Lens Calculator is free to use. By using this site you agree to these terms. If you do not agree with them, do not use the site.

Estimates only, not a prescription

The calculator converts a glasses prescription using the vertex-distance formula, a standard optometry calculation. The result is an estimate and is not a valid contact lens prescription. Glasses and contact lens prescriptions are different documents: contact lenses also require a base curve, diameter and a fitting from an eye care professional that this calculator does not provide.

Always confirm any converted value with your optometrist or ophthalmologist, and order contact lenses only against a valid prescription from that professional.

No warranty

This site and its calculators are provided as-is, without warranty of any kind. We do not guarantee that results are error-free or fit for any particular purpose, and we are not liable for any decision made based on them.

Acceptable use

Do not attempt to disrupt the site, scrape it at a rate that affects other visitors, or use it for any unlawful purpose.

Affiliate links

Some links on this site are affiliate links, disclosed on the affiliate disclosure page. Following one is optional and does not change what the calculator shows you.

Changes to these terms

These terms may be updated from time to time. Continued use of the site after a change means you accept the updated terms.