Getting the right CPAP mask size comes down to measuring a few specific points on your face and matching those measurements to the manufacturer’s sizing guide. The process differs slightly depending on whether you’re fitting a nasal mask, a full-face mask, or nasal pillows, but each takes only a few minutes with the right tools.
Why Sizing Matters
Air leakage is the most commonly reported side effect of CPAP therapy, and a poorly sized mask is one of the main causes. Roughly one-third of CPAP users report nasal symptoms and dry mouth, and mask-related problems like poor fit and leakage affect about 12% of users at the three-month mark. Leaks don’t just make the mask uncomfortable. They reduce the air pressure your machine delivers, which means your therapy becomes less effective. Persistent leaks are also linked to lower adherence, meaning people are more likely to stop using their CPAP altogether.
A mask that’s too large will shift around on your face and leak air, often directing it toward your eyes. A mask that’s too small presses into the skin, causes red marks, and can still leak because the cushion can’t form a proper seal against your facial contours.
What You’re Actually Measuring
Each mask type sits on a different part of your face, so the landmarks you measure change depending on the style.
For a nasal mask, you’re measuring the width of your nose and the vertical distance from the bridge of your nose down to the area between your upper lip and the base of your nostrils (called the philtrum). The bridge of your nose sets the top boundary, and the space just above your upper lip sets the bottom.
For a full-face mask, the measurement area is larger. You’re capturing the distance from the bridge of your nose down to just below your lower lip, including the chin crease. Width-wise, you need to account for the broadest part of your face where the mask cushion will rest, typically along the sides of your nose and out toward your cheeks.
For nasal pillows, the measurement is much simpler. You’re sizing based on your nostril width and the tip of your nose. The pillows insert slightly into or rest against the nostrils, so the key dimension is how wide your nostrils are at their outer edges.
How to Use a Printable Sizing Template
Most major manufacturers, including ResMed and Philips, offer printable PDF sizing templates for their masks. These are the most reliable way to size yourself at home, but they only work if you print them correctly.
Open the PDF and print it at exactly 100% scale. Do not select “fit to page” or “shrink to fit,” as this will resize the template and throw off your measurement. Every template includes a printed ruler or reference bar on the page. After printing, hold a real ruler up to that reference image. If the measurements match, your printout is accurate. If they’re off by even a millimeter or two, adjust your print settings and try again.
Once you’ve confirmed the scale is correct, cut out the template along the dotted lines. For nasal and full-face masks, fold and position the cutout against your face as the instructions direct. Align the bottom edge between your upper lip and nose (for nasal masks) or below your chin crease (for full-face masks), then use the bridge of your nose as your top reference point. The template will show size indicators where these landmarks fall.
For nasal pillows, the Philips DreamWear guide instructs you to fold the template, cut out the fitting gauge, and place it against your nose. Your size is determined by where the outer edges of your nostrils and the tip of your nose contact the gauge. If you fall between sizes, go with the smaller option. Philips specifically recommends using the smallest cushion that fits your nose for the best seal.
If You Fall Between Sizes
It’s common to land between two sizes on a template. ResMed’s fitting instructions for their full-face masks note that if your chin crease falls between sizes, you should choose the smaller size. This general principle holds across most mask types: a slightly snug cushion that conforms to your face will seal better than a larger one that gaps around the edges. You can always loosen headgear straps to reduce pressure from a smaller cushion, but you can’t tighten your way out of a mask that’s fundamentally too large.
Sizing Is Not Universal Across Brands
A medium in one brand is not necessarily a medium in another. Each manufacturer designs their cushions around different facial geometry, uses different materials, and defines their size ranges independently. A ResMed medium and a Philips medium may fit quite differently on the same face. Always use the specific sizing template or fitting guide from the manufacturer of the mask you’re buying. If no template is available, measure the width of your nose (for nasal masks) or the distance between the key facial landmarks described above and compare those numbers to the brand’s published size chart.
Facial Hair and Mask Fit
Facial hair complicates the seal for any mask that rests against skin. How much it matters depends on the mask type and where your hair grows.
Nasal pillows are the most facial-hair-friendly option. Since they sit at the nostrils rather than forming a seal across larger areas of your face, a beard or mustache generally won’t interfere. Nasal masks can work with most beards, but a thick mustache may prevent the bottom edge of the cushion from sealing properly against the skin above your upper lip. Full-face masks are the most affected, because the cushion needs uninterrupted contact from the bridge of your nose all the way around your mouth and chin. Depending on where the mask’s edge lands, you may need to trim or shave a narrow strip along that seal line.
If shaving isn’t an option, cloth mask liners can help. These accessories flatten facial hair beneath the cushion and create a smoother surface for the mask to seal against. They’re not a perfect substitute for bare skin, but they can make a meaningful difference for people who want to keep their beard intact.
When measuring with facial hair, take your measurements on the skin itself, not over the hair. The template needs to read your actual bone structure and tissue dimensions. Facial hair doesn’t change your mask size, but it may change which mask style works best for you.
Checking Your Fit After You Order
A sizing template gets you in the right range, but the real test happens when you put the mask on with your CPAP running. Put the mask on while lying in your normal sleeping position, not sitting upright. Your facial tissue shifts with gravity, and a mask that feels fine while you’re sitting up may leak when you’re on your side or back.
Turn the machine on and breathe normally. You should feel consistent pressure without air blowing against your eyes or escaping around the edges of the cushion. Most CPAP machines track leak rates and will flag excessive leakage in their app or on-screen display. If your leak rate is consistently high, the cushion size may be wrong, or you may need to adjust the headgear tension. Tighten straps only enough to stop the leak. Over-tightening is one of the most common mistakes and leads to skin irritation and pressure sores on the bridge of the nose.
If you’ve tried adjusting straps and the leak persists, try the next size up or down before switching to a completely different mask. Small changes in cushion size often solve problems that seem like they need a whole new approach.