REM Sleep Calculator

1. Enter when you went to bed and woke up. Nights across midnight work automatically.
2. Add how long it took to fall asleep. The estimate is based on your time asleep, not time in bed.
3. Optional: add your tracker numbers. The calculator shows them as a share of your sleep so you can compare them with typical values.

REM (rapid eye movement) sleep is the stage when most dreaming happens. The brain is very active, the eyes move quickly behind closed lids and most muscles are temporarily relaxed. The rest of the night is non-REM sleep, which has three stages: light stage 1, stage 2, and stage 3, the deep or slow-wave sleep you need to feel refreshed.

You move through non-REM and REM several times a night, as the next section explains.

For a fuller tour of each stage, read the stages of sleep, and for dreaming, how sleep cycles affect your dreams.

REM first occurs about 90 minutes after you fall asleep. You then cycle through non-REM and REM several times, and NINDS describes increasingly longer, deeper REM periods later in the sleep session. The Sleep Foundation puts it the same way: with each new cycle you spend more time in REM, so most REM sleep takes place in the second half of the night.

That is why the calculator shows your longest REM window as the last third of your sleep, and why an early alarm removes REM first.

It works out your time asleep, then applies the typical share of each stage and the typical timing of REM.

The REM share is a textbook value for healthy young adults; the deep sleep range is the adult range from the Sleep Foundation. Real nights vary, and the shares of deep sleep and REM fall with age.

Waking at 5:30 AM instead would cut out much of that last-third window, which is why short nights cost REM sleep in particular. To plan a wake-up at the end of a cycle, use the sleep cycle calculator.

No source we checked gives a full REM table by age, so the rows below use only what NINDS, the Sleep Foundation, StatPearls and a lifespan meta-analysis state.

The calculator uses the adult 25% share. For a child or an older adult, treat its REM figure as an upper guide rather than a target.

Age

REM falls from infancy through old age (see the REM by age table), and deep sleep falls with it in adults.

Sleep Length

Short nights cut REM more than deep sleep, because REM is concentrated toward morning.

Alcohol And Some Medicines

Both can change how much time you spend in each stage. Ask a doctor or pharmacist about your medicines.

Regular Timing

An irregular schedule shortens and fragments sleep, which leaves less time for every stage.

• Sleep tracker users wondering whether their REM or deep sleep numbers are normal.
• People who wake early and want to know what they are missing.
• Anyone curious about dreams and when they happen in the night.
• People cutting sleep short who want to see the effect on REM.

Treating Tracker Stages As Exact

Watches and rings estimate stages from movement and heart rate. Only a sleep lab study measures them directly.

Chasing A Perfect Percentage

Stage shares vary night to night. Look at weeks, not single nights.

Ignoring Total Sleep

The surest way to get more REM and deep sleep is enough total sleep; check it with the sleep duration calculator linked below.

Comparing With A Young Adult

Lower deep sleep and REM shares are normal as you get older.

The calculator gives estimates from typical stage shares and timing. It cannot measure your sleep stages.

Healthy adults typically spend about a quarter of their sleep in REM, around 1.5 to 2 hours in a 7 to 8 hour night.

Adults typically spend 10% to 20% of the night in deep sleep, which falls with age. Older adults normally get less.

The first REM period starts about 90 minutes after falling asleep, and REM periods get longer toward morning.

The longest REM periods come in the last part of the night, so waking early removes more REM than deep sleep.

They are estimates from movement and heart rate. Use them for trends rather than exact values.

Most adults complete 4 to 6 cycles of about 90 to 110 minutes in a full night.

Most dreaming happens in REM, although some dreaming also occurs in non-REM sleep.

Get enough total sleep, keep a regular schedule and avoid alcohol close to bedtime.

• StatPearls: Physiology, Sleep Stages (stage shares, 90 to 110 minute cycles)
• NINDS: Brain Basics: Understanding Sleep (first REM at about 90 min, longer REM later)
• Sleep Foundation: REM sleep (adults about 2 h of REM, newborns about 8 h a day, more REM in later cycles)
• Sleep Foundation: Deep sleep (adults typically spend 10% to 20% of the night in deep sleep)
• Ohayon et al. Meta-analysis of quantitative sleep parameters across the lifespan (Sleep, 2004) (deep sleep and REM fall with age)