How to Work Out Contact Lens Prescription from Glasses: Your Complete UK Guide

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         How to Work Out Contact Lens Prescription from Glasses: Your Complete UK Guide   March 18, 2026   
             SEO Tapita 

        You cannot directly use your glasses prescription to order contact lenses. While conversion charts can estimate power for prescriptions under ±4.00 (usually the same power), higher prescriptions require vertex distance adjustment. Contact lenses also need base curve, diameter, and brand specifications that glasses prescriptions don't include. UK law requires a proper contact lens fitting before purchase.

This comprehensive guide explains exactly how glasses and contact lens prescriptions differ, provides a conversion chart for estimation purposes (with important limitations), addresses colored contact lens considerations, and outlines what you actually need to do to get contacts in the UK. Whether you’re switching from glasses or just curious about the numbers, we’ve got you covered.

Can You Use Your Glasses Prescription for Contacts?

No, you cannot and should not use your glasses prescription to order contact lenses in the UK. Here’s why this isn’t just opticians being difficult there are legitimate medical, legal, and practical reasons: