Insomnia and 3am waking
Sleep efficiency calculator
Type in up to seven nights from your diary to see what share of your time in bed was spent asleep, for each night and for the week. The result also explains the 85% mark used in CBT for insomnia.
Sleep efficiency is the time you were asleep divided by the time you spent in bed, as a percentage. The Consensus Sleep Diary, the standard diary insomnia researchers agreed on in 2012, defines it exactly that way. CBT for insomnia uses 85% as its working mark: at or above it, time in bed is allowed to grow.
The number matters in menopause because a night broken by sweats often looks fine on the clock. You can spend eight hours in bed and sleep barely six of them. The rest is spent lying awake, and that habit is what CBT-I sets out to break.
Work out your sleep efficiency
Fill in one night or all seven. Leave a night blank to skip it. Count from the moment you got into bed: if you read or scrolled first, add that time to "minutes to fall asleep".
How to calculate sleep efficiency
The calculator uses the Consensus Sleep Diary's formula. Its authors list the measures a diary should give: how long sleep took to arrive, time awake after first falling asleep, total sleep time, time in bed, and sleep efficiency, "the percent of the time asleep out of amount of time spent in bed".
- Time in bed runs from when you get into bed to when you get out of it.
- Time asleep runs from when you get into bed until your final waking, minus the minutes before you dropped off and any time awake during the night.
- Sleep efficiency is time asleep divided by time in bed, times 100.
For the week, the calculator adds up every minute asleep and divides by every minute in bed. That weights a long night more than a short one, and it is the figure to compare with 85%. The mean of the nightly percentages is shown beside it, and the two are usually within a point or two of each other.
A worked example
A made-up reader gets into bed at 10:30pm and lies awake for 40 minutes before she drops off. A night sweat and a bathroom trip keep her awake for an hour in all. She wakes for good at 5:45am and lies there until the alarm at 6:30am.
| Step | Sum | Result |
|---|---|---|
| Time in bed | 10:30pm to 6:30am | 8 h 0 min |
| Bed to final waking | 10:30pm to 5:45am | 7 h 15 min |
| Time asleep | 7 h 15 min less 40 min and 60 min | 5 h 35 min |
| Sleep efficiency | 335 min divided by 480 min | 70% |
To reach 85% with eight hours in bed she would need about 6 hours 48 minutes of sleep. The 45 minutes after her last waking cost her more than nine points on their own, which is why the time between waking and getting up has its own box.
Time in bed vs time asleep: what the 85% mark means
The American Academy of Sleep Medicine guideline on behavioural treatments for chronic insomnia gives its only strong recommendation to multicomponent CBT-I. It describes that as cognitive work plus education about sleep, stimulus control and sleep restriction therapy, steered by sleep diaries kept through a course of typically 4 to 8 sessions. Sleep restriction, in the guideline's words, limits time in bed to your average sleep, then moves it up or down "based on sleep efficiency thresholds".
Stanford Health Care's description of the method gives the numbers. Time in bed starts at your average nightly sleep over the last week, never under 5.5 hours. Each setting is kept for at least a week. If the week's average efficiency is 85% or more, time in bed grows by 15 to 30 minutes. Below 80% it is cut further, and in between it stays put. Stanford adds that there are several versions and the therapist chooses one to fit the patient.
So 85% is a decision point inside a treatment, used week after week. It is not a pass mark for one night, and a score under it does not tell you what is wrong. Pain, a full bladder, sleep apnoea or a hot bedroom can all pull the number down, and the guideline says treatment should start with a proper diagnosis.
Why this number helps in menopause
The National Institute on Aging says CBT for insomnia has been shown to improve sleep in women with menopausal symptoms, and suggests a therapist who has worked with women going through the transition. In the MsFLASH trial, described in our article on menopause insomnia, the CBT-I sessions for women with hot flashes included sleep restriction, so a week of efficiency figures is the kind of record such a course starts from.
It also separates two problems that feel alike at 4am. If your efficiency is high but your time in bed is short, you may simply be giving sleep too little room, and the bedtime wind-down planner helps you set a steady window. If your time in bed is long and your efficiency is low, most of the lost time is spent lying awake. Our article on waking at 3am in menopause describes that pattern.
My take
I'd collect a full week before reading anything into the result, using the printable night diary each morning while the night is still fresh, and I would be honest about the time spent awake after the last waking. That stretch is the easiest to leave out and the one that moves the percentage most. If the week comes in under 80%, I'd take the printout to a doctor and ask whether CBT-I is available, rather than shortening my nights alone. The doctor questions builder has that question ready.
Everything else we have written on broken nights is under insomnia and 3am waking.
When to see a doctor
The NHS suggests seeing a GP if changing your sleep habits has not worked, if you have had trouble sleeping for months, or if it is making daily life hard to cope with. A GP may offer CBT for insomnia face-to-face or as an online self-help programme.
This calculator works out an estimate from times you remember, using the Consensus Sleep Diary formula. It does not diagnose insomnia or any other sleep problem, and it does not replace a doctor or a CBT-I therapist.