Find your Perfect Prescription Mask

Mask Size Guide Helper

Measuring Your Face

Steps to Measure

  1. Face Width: Measure from the outer corner of one eye to the outer corner of the other.
  2. Face Height: Measure from just below your nose to just above your eyebrow line.
  3. Compare: Match your width and height to the mask charts below. Aim to be between Min and Max.

Quick Face-Width Checker

Use a straightedge ruler to measure across your face from outer eye to outer eye (where the eye slits end). Use this as a quick size cue, then confirm with the charts below.

Width (in) Width (cm) Suggested Category
Under 4.00" Under 10.2 cm Small
4.00" – 4.50" 10.2 – 11.4 cm Standard / Medium
Over 4.50" Over 11.4 cm Large

Optional Head-Size Check

Quick tip: Wrap a string around your head along your normal hat line (above ears/brows), mark where it meets, then measure the string. Use the table below as a rough proxy for Small / Medium / Large, then confirm with face measurements.

ORDER SIZE HEAD SIZE METRIC CM US INCHES
SMALL 6⅜ – 6⅞ 54 – 55 21¼ – 21½
MEDIUM 7 – 7⅛ 56 – 57 21⅞ – 22¼
LARGE 7¼ – 7⅜ 58 – 59 22⅝ – 23
X-LARGE 7½ – 7⅝ 60 – 61 23½ – 23⅞

Head circumference is a rough guide—always confirm with the face width/height charts below.

Measurement tips: Use a straight ruler (don’t bend or wrap it around your face), keep it level using a mirror, and ask someone to help if possible.

Rx Lens Strength + Face Fit

Find Your Prescription Mask Quiz

Built specifically for prescription snorkel and dive masks, this quiz helps match your lens strength, face fit, and intended use in one simple flow.

Answer up to 6 quick questions in about 2 minutes.

Start the quiz →

Have your prescription nearby if you know your numbers. If not, no problem, we can still guide you.

Lens strength Face fit Snorkel or dive
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Your prescription image is only used to read your values. It is never stored.

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Use Our Exclusive Underwater Lens Calculator Tool

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

[−] minus for Myopia (nearsighted), [+] plus for Hyperopia (farsighted).
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Right CYL Check your CYL value and its + or − sign. Select 0.00 if you have no astigmatism.
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Left CYL
Your Recommended Underwater Lens Strength
Right (OD)
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Left (OS)
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This is your recommended starting strength. If unsure, email us your prescription and we will confirm.