Under-mattress sleep tracker: how it works and how accurate it is
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- Withings Sleep under-mattress tracker. Best for: People who want sleep and snoring tracking without wearing anything. See options on Amazon
- Contactless under-sheet sleep monitor. Best for: Buyers comparing other non-wearable trackers. See options on Amazon
- Smart ring sleep tracker. Best for: People who do not mind wearing a device and want daytime data too. See options on Amazon
How an under-mattress tracker works
Withings describes its Sleep pad as having a pneumatic sensor that measures heart rate, breathing rate and movement through the mattress using ballistography, plus a sound sensor that identifies snoring and breathing disturbances. It lists metrics including sleep duration, sleep onset and time to wake, deep, light and REM phases, heart rate, snoring duration and a sleep score.
Because nothing touches your body, there is nothing to remember to put on. Withings says the pad suits all sleep positions and needs no charging; it runs from the included USB power adapter. If you would rather wear a device, see our smart ring sleep tracker guide.
How accurate are they?
| Measure | Withings Sleep Analyser vs sleep lab |
|---|---|
| Sleep vs wake accuracy | 83% overall |
| Detecting sleep (sensitivity) | 95% |
| Detecting wake (specificity) | 37% |
| Total sleep time | Overestimated by an average of 48 minutes |
| Wake after falling asleep | Underestimated by an average of 54 minutes |
Figures are from a 2025 study of 183 adults comparing the Withings Sleep Analyser with polysomnography, the lab standard. The authors found performance comparable to other consumer sleep trackers, with high sensitivity but poor specificity: it is good at spotting sleep and poor at spotting time awake in bed.
Who it works best for
The same study found accuracy was higher for healthy people, 89%, than for people with sleep disorders, 81%. It was also higher for night sleep than for daytime sleep in healthy people. The authors noted the tendency to overestimate sleep, particularly where wake time is high.
So an under-mattress tracker is most useful for people without a sleep disorder who want to see patterns over weeks. If you lie awake a lot, it may tell you that you slept more than you did.
A larger 2023 study of 11 consumer sleep trackers, including a Withings mat, found sleep-stage agreement with lab tests varied widely between devices, with the best macro F1 score at 0.69 and the lowest at 0.26. The study collected 3890 hours of tracker recordings from 75 participants.
Setup and requirements
- Size. Withings lists its pad at 637 mm (25 in) long, 190 mm (7.5 in) wide and 5 mm (0.2 in) thick.
- Power. A 5V 1A USB power adapter is included; it stays plugged in.
- Connection. Bluetooth for installation and 2.4 GHz Wi-Fi for automatic sync.
- Phone. Setup is done on a smartphone or tablet through the Withings app; it cannot be set up from a computer.
- Mattress. Withings says it is not intended for water mattresses.
- Subscription. Withings sells an optional subscription for extra features; check what is included without it.
Snoring and breathing: what it can and cannot tell you
Withings lists snoring duration and says its sound sensor identifies breathing disturbances. Treat these as prompts, not answers. Loud snoring, pauses in breathing or daytime sleepiness are reasons to talk to a doctor, who may order a sleep study. A consumer tracker cannot replace that test.
Withings also says its pad was tested against polysomnography with sleep physicians, which matches the independent study above showing reasonable but imperfect agreement.
Getting useful data
- Place the pad exactly where the maker's installation guide says.
- Keep it plugged in and on Wi-Fi so it can sync.
- Look at weekly trends rather than one night.
- Expect it to count quiet time awake in bed as sleep sometimes, as the study found.
- Pair the data with simple habits, such as a regular bedtime, rather than chasing a perfect score.
What to look for when you buy
Withings Sleep under-mattress tracker
Best for: People who want sleep and snoring tracking without wearing anything
Withings lists ballistography and sound sensors, sleep stages, heart rate and snoring duration, and the Sleep Analyser was tested against polysomnography in a 183-person study.
Watch out: Overestimated sleep by an average of 48 minutes in that study. Needs constant power and Wi-Fi.
See options on AmazonContactless under-sheet sleep monitor
Best for: Buyers comparing other non-wearable trackers
Other contactless under-sheet and under-mattress monitors are widely sold.
Watch out: Look for published validation against polysomnography before trusting the numbers.
See options on AmazonSmart ring sleep tracker
Best for: People who do not mind wearing a device and want daytime data too
Rings track sleep with sensors on the finger and also record daytime activity.
Watch out: Must be worn and charged; see our smart ring guide.
See options on AmazonQuestions people ask
- Do under-mattress sleep trackers work?
- Reasonably for trends. One tested model was 83% accurate for sleep vs wake but overestimated total sleep time by an average of 48 minutes.
- Is an under-mattress tracker better than a watch?
- Not necessarily more accurate; a 2023 study found wide variation across all tracker types. It is easier because you wear nothing.
- Does it work with two people in the bed?
- Check the maker's guidance; place the pad under your own side as instructed.
- Can it detect sleep apnea?
- Do not rely on it. Talk to a doctor about snoring, breathing pauses or daytime sleepiness.
- Does it need charging?
- Withings says no; the pad plugs into a USB power adapter.
Sources
- Sleep (withings.com), Withings
- Performance evaluation of an under-mattress sleep sensor versus polysomnography in > 400 nights with healthy and unhealthy sleep (pmc.ncbi.nlm.nih.gov), Journal of Sleep Research (PMC12592840)
- Accuracy of 11 Wearable, Nearable, and Airable Consumer Sleep Trackers: Prospective Multicenter Validation Study (pmc.ncbi.nlm.nih.gov), JMIR mHealth and uHealth (PMC10654909)