Snorkel mask size chart: how to measure your face
By SnorkelMatch, last checked . How we check
Full-face snorkel masks are sized by one length: from the bridge of your nose to the bottom of your chin. Here is how to measure it in a minute, and every maker's chart we could read on its own website, side by side in inches and centimeters.
What you need
A straight ruler, a mirror, and a minute. A ruler marked in both inches and centimeters helps, because the makers publish their charts in centimeters and we show both. If you only have a soft tape measure, hold it straight and flat rather than letting it follow the curve of your face.
How to measure, step by step
- Stand in front of a mirror, look straight ahead and close your mouth without clenching.
- Find the bridge of your nose: the dip between your eyes, roughly level with your pupils. Put the zero of the ruler there.
- Hold the ruler straight down along the middle of your face and read it at the bottom edge of your chin, not along the jawline.
- Measure a second time. If the readings differ by more than a tenth of an inch, measure a third time and use the middle value.
The makers word the measurement slightly differently. Ocean Reef says “from your nose bridge, to the bottom of your chin”[1]; Cressi says “from the chin to the eye line”[2]; Decathlon says “the distance between your chin and your eyes”[4]. All three point to the same two landmarks, which is why one measurement works across the charts.
The size lines, maker by maker
These are the published charts as we read them on each maker’s website. The values are in centimeters because that is how the makers publish them; the inches are our conversion.
- Ocean Reef Aria QR+, Aria Classic, Aria JR: XS below 3.9 in (10.0 cm); S/M 3.9 in (10.0 cm) to 4.5 in (11.5 cm); M/L 4.5 in (11.5 cm) to 4.9 in (12.5 cm); L/XL 4.9 in (12.5 cm) to 5.5 in (14.0 cm).
- Cressi Duke, Duke Action, Baron: S/M 3.9 in (10.0 cm) to 4.7 in (12.0 cm); M/L from 4.7 in (12.0 cm).
- Cressi Kiddy: One size 3.3 in (8.5 cm) to 3.9 in (10.0 cm).
- Decathlon (Subea) Easybreath (adult surface masks): S/M below 4.7 in (12.0 cm); M/L from 4.7 in (12.0 cm).
Ocean Reef’s chart covers its XS kids’ model and its adult models, with M/L only for the Aria QR+[1]. Cressi’s adult chart starts at 10 cm (4 in) and its separate Kiddy chart covers 8.5 to 10 cm for ages 6 to 12, for users 25 kg (55 lb) and over[2][3]. Decathlon has two adult sizes split at 12 cm (4.7 in)[4].
Your measurement on every chart
This table is produced by the same code as the size finder, so the two never disagree. “Near” means you are within half a centimeter (about 0.2 inch) of a size line.
| Length | Ocean Reef Aria QR+, Aria Classic, Aria JR | Cressi Duke, Duke Action, Baron | Cressi Kiddy | Decathlon (Subea) Easybreath (adult surface masks) |
|---|---|---|---|---|
| 3.4 in (8.6 cm) | XS | below chart | One size | S/M |
| 3.6 in (9.1 cm) | XS | below chart | One size | S/M |
| 3.8 in (9.7 cm) | XS (near S/M) | below chart | One size | S/M |
| 4.0 in (10.2 cm) | S/M (near XS) | S/M | above chart | S/M |
| 4.2 in (10.7 cm) | S/M | S/M | above chart | S/M |
| 4.4 in (11.2 cm) | S/M (near M/L) | S/M | above chart | S/M |
| 4.5 in (11.4 cm) | S/M (near M/L) | S/M | above chart | S/M |
| 4.6 in (11.7 cm) | M/L (near S/M) | S/M (near M/L) | above chart | S/M (near M/L) |
| 4.7 in (11.9 cm) | M/L (near S/M) | S/M (near M/L) | above chart | S/M (near M/L) |
| 4.8 in (12.2 cm) | M/L (near L/XL) | M/L (near S/M) | above chart | M/L (near S/M) |
| 5.0 in (12.7 cm) | L/XL (near M/L) | M/L | above chart | M/L |
| 5.2 in (13.2 cm) | L/XL | M/L | above chart | M/L |
| 5.4 in (13.7 cm) | L/XL | M/L | above chart | M/L |
| 5.6 in (14.2 cm) | above chart | M/L | above chart | M/L |
Why two brands give you different sizes
Each maker draws its own lines. Ocean Reef splits S/M and M/L at 11.5 cm (4.5 in), while Cressi and Decathlon split at 12 cm (4.7 in)[1][2][4]. A face of 4.6 inches (11.7 cm) is M/L on Ocean Reef’s chart but S/M on Cressi’s and Decathlon’s. Size labels are not a shared standard: read the chart for the exact mask you are buying.
When you land near a line
A tenth of an inch of ruler slip can move you across a line. Measure again, then try both sizes if you can. Ocean Reef’s chart itself says “Try the mask on to be sure of fit”[1], and Cressi calls its chart “a reference only”[2]. Online, check the return policy first and keep the packaging until the mask passes the seal test. Decathlon’s check for a full-face mask is simple: there should be no space between the silicone skirt and your chin[4].
Children’s sizes
Measure a child the same way. The kids’ sizes we found are Ocean Reef’s XS (below 10 cm, Aria JR only) and Cressi’s Kiddy (8.5 to 10 cm, ages 6 to 12, 25 kg and over)[1][3]. Decathlon describes its S/M as suitable for children above the age of 10[4]. Follow each maker’s age and size guidance, and read our kids’ guide for supervision.
Traditional masks have no size chart
Two-strap masks with a separate snorkel are sold differently. The official stores we checked list adult models as one size, such as a mask with “a one-size-fits-all design”, and kids’ models by age, such as “Designed for ages 6+”[5]. For those, the fit test is the size test: hold the mask on without the strap, breathe in gently through your nose and let go. DAN says a mask that fits “should seal to your face and not fall off even without the mask strap in place”[6].
Sizes are the makers' published charts as read on 2026-10-09; makers can change them. Fit varies with face shape, so try the mask on and check the seller's return policy before you buy. We do not guarantee fit. Brand names belong to their owners; no affiliation, sponsorship or endorsement.
Questions people ask
How do you measure your face for a snorkel mask?
Put the zero of a ruler at the bridge of your nose, in the dip level with your eyes, and read it at the bottom of your chin, mouth closed, looking straight ahead. That nose-bridge-to-chin length is what the full-face size charts use.
What size snorkel mask do I need for a 4.5 inch face?
On the charts we compiled, 4.5 inches (11.4 cm) is S/M for Ocean Reef, Cressi and Decathlon, and it sits close to Ocean Reef's line between S/M and M/L at 11.5 cm. Close to a line, try both sizes if you can.
Is S/M or M/L the normal adult size?
Decathlon describes M/L as the average size of an adult and S/M as for adults with a narrow face, women and children above the age of 10. Other makers do not put it that way; your measurement against that maker's own chart decides.
Do I need face width?
None of the full-face charts we read use face width. It can help you compare skirt widths when a seller lists them for a traditional mask, but the seal test decides the fit.
Can I measure with a tape measure or a phone?
A straight ruler held flat against the face is easiest to read. A soft tape follows the curve of the face and can read long. Measure twice; if the two readings differ, use the average and treat it as borderline.
Sources
- [1]Ocean Reef (manufacturer): Aria QR+ size chart
Measure "from your nose bridge, to the bottom of your chin"; XS (kids) up to 10 cm, S/M 10-11.5 cm, M/L 11.5-12.5 cm (Aria QR+ only), L/XL 12.5-14 cm; "Try the mask on to be sure of fit". Read on 2026-10-09.
- [2]Cressi (manufacturer): Duke full face mask size chart
"use a ruler to measure from the chin to the eye line"; S/M 100-120 mm (4-4 3/4 in), M/L over 120 mm (over 4 3/4 in); "to be used as a reference only". Read on 2026-10-09.
- [3]Cressi (manufacturer): Kiddy full face mask size chart
Ages "6-12, for users 25 kg+", height 8.5-10 cm (3.35-3.94 in). Read on 2026-10-09.
- [4]Decathlon (manufacturer): A Guide to Selecting the Perfect Size for Your Easybreath Mask
Measure "the distance between your chin and your eyes": less than 12 cm (4.7 in) S/M, more than 12 cm M/L; "If there's no space between the silicone skirt and your chin, then this is the mask for you." Read on 2026-10-09.
- [5]U.S. Divers (manufacturer): Snorkeling masks collection
An adult mask "features a one-size-fits-all design"; kids' models are labelled "Designed for ages 6+" and "Designed for ages 4+". Read on 2026-10-09.
- [6]Divers Alert Network (DAN): Mask Squeeze (Facial Barotrauma)
"You should be able to achieve an appropriate seal by gently placing the mask on your face and inhaling through your nose. The mask should seal to your face and not fall off even without the mask strap in place. It is not unusual for a small amount of leakage to occur while diving, especially if you have facial hair." Equalizing a mask means "adding air to the space in the mask (by exhaling through your nose)". Read on 2026-10-09.
Related guides
- How a snorkel mask should fit: the 30-second seal test at homeThe no-strap sniff test, what a good fit feels like, where leaks come from and how tight the strap should be, before you ever get in the water.
- Snorkel masks for kids: fit and supervision checklistMeasuring a child, the makers' kids' sizes and age notes, what a 2025 case series reported about young children, and the CDC's supervision rules.
- Full-face vs traditional snorkel mask: how to chooseHow each type is built, how you breathe in it, and which one suits a beard, glasses, a gag reflex, a child or a weaker swimmer, with sources.
- How to choose a snorkel mask: a step-by-step guideMeasure, pick a type, read your size on the maker's chart, test the seal and practice on land: the whole decision in order, with links to each detail.
Last checked October 9, 2026. General information from official sources, not medical, safety-training or professional advice. Snorkeling carries real risks, including drowning: never snorkel alone and follow the manufacturer's instructions and local lifeguard guidance.