How to Measure Your Pupillary Distance (PD) at Home

Pupillary distance (PD) is the distance in millimeters between the centers of your pupils. Online glasses retailers (Warby Parker, Zenni, EyeBuyDirect) all require it, and most prescriptions do not include it. Here are three accurate ways to measure your own PD at home.

Why PD Matters

PD determines where the optical center of each lens sits in your frame. Wrong PD means lens optical centers misaligned with your pupils, leading to eyestrain, headaches, and blurriness, especially with progressive or high-prescription lenses. For single-vision glasses under plus or minus 2.00 diopters, small PD errors (1 to 2 mm) usually do not matter. For higher prescriptions or progressive lenses, accurate PD is essential.

Normal PD Ranges

• Adult women: typically 54 to 66 mm (average about 62 mm)
• Adult men: typically 58 to 70 mm (average about 64 mm)
• Children: 41 to 55 mm (changes with age)
• Near PD (for reading glasses): 3 to 4 mm less than distance PD because the eyes converge inward when looking close

If your measured PD is far outside these ranges, re-measure or have it checked professionally.

Method 1: The Mirror Method (30 seconds)

1. Stand about 8 inches (20 cm) from a mirror under bright, even light.
2. Hold a millimeter ruler horizontally against your brow with the 0 mark above your right pupil.
3. Close your right eye and look at your left pupil in the mirror with your left eye.
4. Without moving the ruler, note the mm mark above the center of your left pupil. That number is your PD.
5. Repeat twice and average the three readings.

You can use our online millimeter ruler to verify a paper ruler before measuring.

Method 2: Photo Method (Most Accurate)

1. Tape a standard credit card horizontally to your forehead (printed side out). Cards are exactly 85.6 mm wide. They serve as a built-in scale.
2. Stand 3 to 4 feet from a friend or a phone tripod.
3. Look at the camera with a relaxed, neutral expression. Take a photo.
4. In any photo editor, measure the pixel distance between pupils, then the pixel width of the credit card.
5. PD equals (pupil distance in pixels divided by card width in pixels) × 85.6 mm

This is more accurate than the mirror method because there is no reflective offset.

Method 3: Friend and Ruler

1. Sit facing a friend with your eyes at roughly the same level.
2. Have them hold a mm ruler horizontally just below your eyes, resting it on the bridge of your nose.
3. Look straight ahead, focused on a point about 20 feet away (a wall poster).
4. Friend aligns the 0 mark with the center of your right pupil, then reads the mm mark at the center of your left pupil.
5. Repeat 2 to 3 times. Average the readings.

Dual PD vs Single PD

Some opticians measure each eye separately from the bridge of the nose, called "dual PD" or "monocular PD." This is more accurate for people with asymmetric faces. If your dual PD reads as 31/32 mm, your total binocular PD is 63 mm. Most online glasses retailers accept either single (binocular) or dual PD.

Common Mistakes

• Looking at the ruler instead of the mirror. Your eyes converge when looking close, which throws off the measurement by 3 to 4 mm.
• Measuring with eyes crossed. Always focus on a distant point (or a single eye in the mirror with the other closed).
• Using a flexible plastic ruler with a margin before the 0 mark. Use a steel ruler or our calibrated online ruler.
• Rounding aggressively. PD is reported to the nearest 0.5 or 1 mm. Round 62.3 to 62, not 60.
• Holding the ruler at an angle. The ruler must be horizontal and level with your pupils.

When to Get a Professional PD

For high prescriptions (above plus or minus 4.00 diopters), progressive lenses, or if you are getting your first glasses, ask any optician. Most measure PD for free even if you do not buy from them. Take a friend or family member who can help measure if you cannot see clearly without your existing glasses.

Recording Your PD

Once measured, write your PD down with the date. It can change very slightly over years, but for most adults it stays stable. Common ways it is written on a prescription: PD: 63, PD 31/32, or OD 31 / OS 32 (right and left eyes in Latin abbreviations).