For the full breakdown, see our best Sleep Apnea Mask guide.
What Cushion Size Do You Need?
Size comes first, because no amount of strap tension fixes a cushion that doesn’t match your face. Measure with the fitting guide for the specific mask you’re using — the numbers differ by mask type and brand. If you’re picking a new mask, our roundup of the best sleep apnea masks notes how each model fits and seals.
- Full-face masks: measure from the bridge of the nose to the indent on the chin.
- Nasal masks: measure the width of the nose; some fitting guides also factor in top-to-bottom nose height.
Trust the measurement over the guess.
The Step-By-Step CPAP Mask Fitting Routine
Start with the straps loose. Place the cushion on the nose, or over the nose and mouth for a full-face mask, and draw the headgear on evenly so both sides sit at the same tension. Mayo Clinic’s CPAP mask guidance follows the same order: seat the cushion first, then let the machine confirm the fit.
Turn the machine on and check for leaks — many devices include a mask-fit function that runs a quick seal test. If air escapes, readjust in small, even increments on both sides rather than pulling the straps harder. The cushion needs to sit flat, with no creases, and the headgear should lie smooth without twists.
Mask type changes where the cushion sits: a full-face cushion rests across the bridge of the nose and below the lower lip, while a nasal cushion sits under the nose and seals around the nostrils. Keep the cushion centered — a twisted or offset cushion is a common source of edge leaks.
How Tight Should A CPAP Mask Be?
Snug enough that no air escapes, loose enough that the cushion isn’t flattened against your skin.
Fit the mask in the position you actually sleep in. A mask that seals perfectly while you sit up often shifts when you lie down, so test it lying down and reseat the cushion if leaks appear. Both Mayo Clinic and ResMed’s patient guidance recommend the same finishing step: run the machine briefly and confirm the seal instead of judging by feel.
Two things are best left alone. If the mask has a forehead support adjustment dial, clinicians set it to the optimal angle during setup — avoid tinkering with it. And if your mask uses magnetic clips, review the user guide before use if you have any implants or medical devices, since magnets can interact with some of them.
Give yourself a daytime practice session. Do the first fitting while awake, and wear the mask for an hour or two to get used to the feel before your first full night. Keep up with cushion and headgear maintenance too — worn parts change the seal over time, so a mask that fit perfectly at first can start leaking months later.
| Common Mistake | Why It Breaks The Fit | The Fix |
|---|---|---|
| Pulling the straps too tight | Fights the air-pressure seal and distorts the cushion | Loosen, reseat the cushion, adjust both sides in small, even steps |
| Using the wrong cushion size | No strap tension can seal a cushion that doesn’t match your face | Measure with the mask’s fitting guide and swap sizes if leaks persist |
| Fitting only while sitting up | The mask shifts when you lie down, so the seal fails at night | Fit in your usual sleep position and recheck with the machine on |
| Adjusting the forehead support dial | Changes the angle clinicians set during
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