OptiConvert — Glasses to Contacts Calculator

Estimate contact lens power from a glasses prescription using 12mm vertex distance and principal-meridian astigmatism conversion.

ptiConvert is a simple glasses-to-contact lens power estimator that helps you understand how spectacle prescription values may change when converted to the contact lens plane. Using the standard 12mm vertex distance formula, OptiConvert estimates contact lens power from your glasses prescription. For astigmatism, it converts both principal meridians and reconstructs SPH and CYL values for a more clinically grounded estimate. Features: - Convert glasses SPH values to estimated contact lens power - Support CYL and Axis inputs for astigmatism - Uses 12mm vertex distance calculation - Rounds results to standard 0.25D increments - Calculates both right eye (OD) and left eye (OS) - Runs locally in your browser - No account required Important disclaimer: OptiConvert provides educational estimates only. It is not medical advice and does not replace a professional eye exam or contact lens fitting. Contact lenses require professional evaluation of base curve, diameter, lens material, brand suitability, eye health, comfort, and fit. Always confirm with a licensed eye care professional before purchasing or wearing contact lenses.