Ensure your prescription is current (usually within the last 1–2 years). When entering it online: : Refers to your Right Eye . OS (Oculus Sinister) : Refers to your Left Eye . Sphere (SPH) : Indicates the strength of the lens.
: Many online retailers (like Warby Parker or Zenni Optical) offer digital tools where you hold a standard magnetic stripe card (like a library card) against your forehead to help their software scale the measurement. Average Range : Most adults have a PD between 54mm and 74mm . 2. Decode Your Current Frame Measurements buying glasses online measurement
: Stand 8–10 inches away from a mirror. Hold a millimeter ruler against your brow. Align the "0" with the center of your left pupil. The measurement directly over your right pupil is your PD. Ensure your prescription is current (usually within the
: The horizontal diameter of one lens. This determines how the "eyes" of the glasses look on your face. Sphere (SPH) : Indicates the strength of the lens