To measure your face for a mask, you need two key measurements: face length (from the bridge of your nose to just below your bottom lip) and face width (from cheek to cheek). A rigid ruler or flexible tape measure works for both. These numbers tell you whether you need a small, medium, or large mask, whether you’re fitting a cloth mask, a respirator, or a CPAP mask.
What You’ll Need
A rigid ruler or a flexible fabric tape measure is the most reliable tool. A rigid ruler works best for face length because you’re measuring a straight vertical line. A flexible tape measure is more practical for face width since it follows the curve of your cheeks. If you don’t have either, a piece of string held against a ruler works in a pinch.
Some mask manufacturers offer printable sizing templates you can cut out and hold against your face. These are convenient but only work if you print them at exactly 100% scale, with no resizing. Always check the test measurement printed on the template before using it.
How to Measure Face Length
Face length is the single most important measurement for mask sizing. You’re measuring from the bridge of your nose down to the indent on your chin, just below your bottom lip. The bridge of your nose sits at the deepest part of the curve between your forehead and the tip of your nose, usually just below your eye line. The bottom point is not the very tip of your chin but the crease just above it, where your lower lip ends and your chin begins.
Hold a ruler vertically against your face, touching the bridge of your nose at the top. Look straight ahead in a mirror and note where the ruler meets that chin indent. Measure in a straight line, not along the curve of your face. For most adults, this measurement falls somewhere between 4 and 5.5 inches (10 to 14 cm). Children typically measure around 4 inches from nose to chin.
How to Measure Face Width
Face width is measured from one cheek to the other, roughly at the level of your nostrils. The exact points vary by mask type. For a full-face mask, you’re measuring between the widest points of your jaw, near the back corners of your jawbone. For a half-face mask or cloth mask, you’re measuring across the cheeks at nostril height.
Use a flexible tape measure or hold a piece of string across your face, then measure the string against a ruler. Adult face width typically ranges from 5 to 6.5 inches for a half-face measurement. Children’s faces average about 7.5 inches cheek to cheek for a full-width measurement, which is why adult masks gap badly on kids.
Matching Measurements to Mask Sizes
Every manufacturer uses slightly different size ranges, so there’s no universal chart. What matters is checking the specific brand’s sizing guide against your measurements. That said, general adult sizing tends to follow a pattern:
- Small: face length under about 4.5 inches, or a narrower jaw
- Medium: face length between 4.5 and 5 inches
- Large: face length over 5 inches, or a wider jaw
If you fall between two sizes, go with the smaller one. A mask that’s slightly snug creates a better seal than one that’s loose. Gaps along the nose bridge, under the chin, or at the cheeks let unfiltered air through, which defeats the purpose regardless of how good the filter material is.
Measuring for a CPAP Mask
CPAP masks need a more precise fit because they maintain air pressure against your face all night. The measurement process depends on the mask style. A full-face CPAP mask covers both your nose and mouth, so you measure from the bridge of your nose to the indent below your lower lip, the same face length measurement described above. A nasal mask covers only your nose, so you measure from the bridge of your nose to just above your upper lip. Nasal pillow masks, which sit inside your nostrils, are sized by nostril width instead.
Take CPAP measurements while your face is relaxed, not smiling or clenching your jaw. Your facial muscles shift during sleep, and a relaxed expression most closely matches your sleeping face. Many CPAP manufacturers provide printable sizing gauges specific to each mask model. You align an arrow on the template to the bridge of your nose and see which size outline best matches your face. These are more accurate than general measurements because they account for the unique shape of that particular mask’s cushion.
Measuring for N95 and Half-Face Respirators
Respirator fit is more demanding than cloth or surgical mask fit because the seal directly determines how much protection you get. Professional settings require formal fit testing, but you can get a solid starting point at home with two measurements: face length and face width.
For face length on a respirator, you’re measuring from the deepest depression at the top of your nose (where the bridge dips between your eyes) straight down to the bottom of your chin. For face width, measure between the two bony points just in front of your ears, at the top of each ear’s small cartilage flap. Research on respirator fit has found that these two dimensions, along with nose width and jaw width, are the strongest predictors of whether a given respirator will seal properly against your face.
Once you’ve selected a size and put the respirator on, do a quick seal check. For a positive pressure check, cover the exhalation valve with your hand and breathe out gently. If air leaks around the edges, the fit isn’t right. For a negative pressure check, cover the filter inlets with your palms and inhale gently. The mask should pull inward slightly against your face and stay collapsed for about ten seconds. If it holds, the seal is good. If air seeps in, adjust the straps or try a different size.
Tips for a Better Fit
Facial hair is the biggest fit killer. Even a day or two of stubble creates channels along the jawline where air bypasses the filter. If you need reliable protection from a respirator, a clean shave along the seal line makes a measurable difference.
Glasses can also interfere. Frames that sit on the nose bridge push the mask away from your face and create gaps. If you wear glasses with a respirator or N95, look for masks with a moldable nose wire and press it firmly around the bridge of your nose before settling your glasses on top.
Weight changes can shift your mask size. Gaining or losing 10 or more pounds can alter the contour of your cheeks and jawline enough to move you into a different size bracket. If a mask that used to fit well starts feeling loose or tight, re-measure rather than just adjusting the straps.