Sleep Cycle Review: The Phone-Only Sleep Tracker

Sleep Cycle is the app most people picture when they think of sleep tracking, and it earned that place by needing nothing but your phone. Leave it by your bed and it listens through the night, estimates how you slept and wakes you with an alarm timed to a lighter stretch of sleep. Like every app in its category, it estimates, so here’s how far to trust it.

What Sleep Cycle does well

It needs only your phone. By default, Sleep Cycle uses your phone’s microphone, and the company says it estimates your sleep stages mainly from your breathing sounds. You can switch to motion sensing, with the phone on the mattress, instead.

Its smart alarm is free. You set a wake-up window of up to 90 minutes, and Sleep Cycle tries to wake you within it when you seem to be sleeping lightly. The aim is to spare you being jolted out of deep sleep, when grogginess tends to be worst.

Where it falls short

The free version takes a detour. You have to start a Premium trial before you can use the app; the free features stay after you cancel, so set a reminder.

The most interesting data costs extra. Long-term trends, snore and sleep-talk recordings, the full sound library and automatic Apple Watch tracking all need Premium.

The price isn’t clearly published. As of November 2026, the US App Store lists Premium plans from $2.99 to $57.99 without saying which billing period each covers.

It hears the whole room. A phone can pick up a partner’s snoring or a pet’s movement. A watch on your own wrist avoids that.

Accuracy: an estimate, and it says so

Sleep stages are defined by brain activity, which a sleep lab measures with polysomnography. A phone can’t do that, and Sleep Cycle describes its sleep-stage analysis as an estimate, not a medical measurement.

The published checks are thin and dated. A 2017 study in 25 children found the app’s sleep time didn’t line up with polysomnography, and a 2020 study in 21 adults found it wasn’t reliable enough in either microphone or motion mode. Both tested older versions. We found no lab study of its current method, and we haven’t measured it ourselves. Use it for patterns, such as when you fall asleep and how long you sleep, rather than for the light, deep and REM split.

Free vs paid

As of November 2026:

• Free: the smart alarm, nightly analysis and graph, a sleep goal and a few sleep sounds.
• Premium: long-term trends, recordings, the full sound library, heart-rate tracking on iPhone, automatic Apple Watch tracking and weekly reports, with plans listed up to $57.99.

If the smart alarm is what you’re after, the free version is enough.

Who it’s for

• You want to track your sleep without buying or wearing a device.
• You want a smart alarm without paying for one.

Who should skip it

• You already wear an Apple Watch to bed. AutoSleep gives you more detail for a one-time $9.99; see our sleep tracker ranking.
• You want answers about insomnia or sleep apnea. Sleep Cycle’s announced apnea feature isn’t available, and that’s a job for a healthcare professional.

The bottom line

Sleep Cycle is still the easiest way to start tracking your sleep: no wearable, and a free smart alarm. Treat its sleep stages as estimates, and watch the trends rather than any single night.