PD guide

Do I need my PD to buy glasses online?

Many online glasses orders ask for PD, or pupillary distance, because lenses need to be centred for your eyes.

Checked on 26 April 2026Reviewed by UK Glasses Guide editorial teamInformation only
Editorial reviewReviewed and updated by the UK Glasses Guide editorial team.
Source dateChecked on 26 April 2026.
CorrectionsSend a correction if retailer terms, pricing or delivery details have changed.
ImportantInformation only; use an optician for medical or fitting advice.
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Quick answer

PD is the distance between the centres of your pupils. It helps the retailer position the optical centre of each lens. For simple low prescriptions, a small error may be less noticeable, but for stronger prescriptions, larger frames or varifocals, PD matters much more.

If a retailer does not have your PD, it may offer an average value, a measuring tool or support instructions. Treat those as a convenience, not a reason to guess casually.

Lower risk

Low single-vision prescriptions, familiar frame sizes and spare pairs.

Higher risk

Strong prescriptions, varifocals, occupational lenses, driving glasses and large frames.

Best check

Use a measured PD where possible and keep a note of whether it is single or dual PD.

Single PD and dual PD

A single PD gives one total distance. Dual PD gives the distance from each pupil to the centre of the bridge. Dual PD can be more precise, especially where the face is not symmetrical.

Can I measure PD myself?

Some people measure PD at home, but accuracy matters. Use the retailer instructions carefully, repeat the measurement, and ask someone else to help if needed. If the prescription is strong or the glasses are important for driving or work, use professional help.

Ordering spare readersPD still matters, but the practical risk may be lower.
Ordering strong lensesPD accuracy becomes more important.
Ordering varifocalsPD is only one measurement; fitting height and frame fit also matter.
UnsureAsk the retailer or an optician before ordering.

Common PD mistakes

  • Entering centimetres instead of millimetres.
  • Mixing single PD and dual PD.
  • Using an old measurement after changing frame style dramatically.
  • Guessing for a strong prescription.

Compare before ordering

Use this guide with the retailer comparison and checkout checklist so the final basket, support route and return terms are clear.

Compare retailersCheckout checklist
Checked on 26 April 2026. Retailer information, comparison notes and source links are reviewed for buyer relevance, but prices, codes, delivery times and policies can change without notice.

Sources checked

This page is written as buyer information, not optical advice. Check current retailer terms and speak to a qualified optician if your prescription, eye health or fitting needs are complex.