Convert your distance PD to near PD for reading glasses — instant, free, works for single and dual PD.
📖 Calculate Your Near PD
Near PD is needed when ordering reading glasses or bifocals. Your eyes converge inward when reading close up, so your near PD is always smaller than your distance PD.
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✅ Your Near PD
🎉 Got your near PD? Order reading glasses online with confidence!
⚠️Medical Disclaimer: All tools on PDCalculator.net are for educational and informational purposes only. They do not replace professional eye care advice, diagnosis, or treatment. Always consult a licensed optometrist or ophthalmologist before purchasing eyewear or making any changes to your vision correction. Results are based on standard optical formulas and are provided as a general guide only.
📋 What is Near PD and Why Does It Matter?
When you look at something close up (like a book or phone), your eyes rotate slightly inward — this is called convergence. Because of this, the optical centres of your reading glasses need to be slightly closer together than your distance glasses. That's your Near PD.
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Distance PD
Used for distance glasses. Your pupils are relaxed and looking straight ahead at an object far away.
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Near PD
Used for reading glasses. Your eyes converge inward, so near PD = distance PD − 3mm (total) or − 1.5mm per eye.
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Why It Matters
Using the wrong PD for reading glasses causes eye strain, headaches, and blurry close-up vision — even if your prescription is correct.
❓ Frequently Asked Questions
What is the formula for near PD? +
Near PD = Distance PD − 3mm (for total/single PD). For dual PD, subtract 1.5mm from each eye. This is the standard formula used by opticians worldwide, based on the average convergence distance of ~40cm (16 inches) reading distance.
My prescription doesn't have a near PD — is that normal? +
Yes, completely normal. Most distance prescriptions only include the single distance PD. Near PD is only specifically measured for bifocal and progressive prescriptions. For single-vision reading glasses, you simply subtract 3mm from your distance PD.
Do I need near PD for progressive lenses? +
Progressive lenses typically use the same PD as your distance prescription. The lab accounts for convergence in the lens design. However, some online retailers do ask for a near PD — when in doubt, use the −3mm calculation.
Can I use my distance PD for reading glasses? +
Technically no — using distance PD for reading glasses places the optical centres slightly too far apart, causing a slight prism effect that strains your eyes. For mild prescriptions this may not be noticeable, but for stronger reading prescriptions it can cause significant discomfort.