Prescription snorkel dive mask sizing help page

Unlocking the Perfect Fit: Your Guide to Measuring Your Face for a Scuba/Snorkel Mask

Your Guide to Measuring Your Face for a Scuba/Snorkel Mask (Fit Made Simple)

A great seal = great vision. Use this quick guide to measure your face and choose a mask that fits comfortably, whether you’re buying a prescription snorkel mask, a prescription scuba mask, or any diving mask with prescription lenses.

Tools

1) Soft measuring tape (or rigid ruler)

2) Mirror

3) Pen & paper

scuba diver wearing prescription snorkel mask by oceans optics fron view

Step 1: Head circumference (overall size)

Wrap the tape around the brow line, above the ears—like a comfy hat. Keep it level and snug (not tight).

53–55 cm: X Small

55–57 cm: S

57–59 cm: M

59–61 cm: L

Tip: If you’re between bands, start with S/M. Choose M/L if you have broader cheekbones or have felt nose-pocket pressure in smaller masks.

Step 2: Eye width

Measure straight across the face at eye level—outer corner to outer corner—keeping the tape or ruler flat (don’t wrap around the curve of your face). This helps gauge frame width and skirt shape for a reliable seal.

Step 3: Nose-to-brow height

Measure from the bottom of the nose to the top of the brow line. This indicates how much vertical space you need so the nose pocket and frame don’t press uncomfortably.

Fit tips that prevent leaks and fog

Do a quick dry-fit at home: place the mask without the strap, inhale lightly through your nose, if it stays for a moment, the skirt shape matches.

Less squinting = fewer leaks. Pick a size that seals with the lightest inhale.

Soft silicone skirts and tempered-glass lenses improve comfort and durability (all our diving masks with prescription lenses are scuba-rated).

Accuracy checklist

1) Measure twice and average your numbers

2) Keep the tape level at the brow line

3) Record in cm (head) and mm/cm (face measurements)

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Mask sizing: Mask Size Guide Helper

How to Measure Your Face for a Prescription Snorkel & Scuba Mask

Buying a mask online can be tricky — so we built multiple ways to check fit and feel confident the seal will be just perfect.

1

Measure Width

Outer eye corner to outer eye corner in a straight line (don’t wrap).

2

Measure Height

From just under your nose to just above your eyebrow line.

3

Optional: Head Size

Wrap a string around your hat line, mark, then measure. Use the table as a guide.

4

Enter Your Sizes

Use our slider tool to enter your measurements & find your perfect fit.

How to measure your face for a prescription mask

Quick Face-Size Checker

Tips: use a straight ruler (don’t bend it), check in a mirror, or ask a friend to help.

3 Head-Size Checker (Optional)

Measure around the hat line (above ears/brows)

Head-Size to Mask-Size

Measure your head the same way you’d measure for a hat. Use a soft tailor’s tape (or wrap a piece of string/cord), around your head above the ears and just above the eyebrows, then read the length (or measure the string). Keep it level all the way around.

4 Enter Your Sizes
Use the slider to find your perfect fit!
Underwater Lens Calculator

Underwater, light bends differently and can make your usual prescription feel too strong.
We lower it slightly to prevent overmagnification and keep your vision clear.
Step 1: Enter your prescription to determine your recommended underwater vision

Choose the sign first:
Use for myopia, + for hyperopia.
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Suggested Lens Strength:

Right
Left