Health Calculators
Sleep Restriction Therapy Calculator
This calculator estimates the sleep window sleep restriction therapy would set from your sleep diary: your average time asleep becomes the time allowed in bed, with a fixed wake time and a safety floor of five and a half hours. Adjust weekly by sleep efficiency: extend at 85% or above, hold from 80% to below 85%, restrict below 80%.
Calculator
Diary entries for your last N nights. Add earlier nights for a broader average.
Your recorded sleep
No measurements are saved on this device yet.
Diary storage
How Sleep Restriction Therapy Works
SRT limits time in bed (TIB) to better match your average sleep time, which can increase sleep drive and sleep efficiency. The initial window is max(average total sleep time, safety floor), rounded up to the nearest 5 minutes. Each week, TIB is adjusted by sleep efficiency: extend by 15 min if it is at least 85%, restrict by 15 min if below 80%, and hold from 80% to below 85%.
About This Calculator
What It Does
This sleep restriction therapy calculator uses your recent sleep data to estimate a practical sleep window. It calculates bedtime from your fixed wake time, average sleep duration, selected variant, and safety floor. The goal is to consolidate sleep and improve sleep efficiency over time.
Worked Example
If your average total sleep time is 5 hours 42 minutes (342 min) and your fixed wake time is 7:00 AM, the Standard variant rounds the recommendation up to 345 min (5 hr 45 min). Bedtime = 7:00 AM - 5 hr 45 min = 1:15 AM.
Real-World Usage
A person with chronic insomnia who averages 5 hours of sleep but spends 8 hours in bed might use this calculator to set a careful first sleep window. After a week, they recalculate: if efficiency exceeds 85%, the window extends by 15 minutes. If below 80%, it restricts further.
Local Context
In Germany, CBT-I methods are used in behavioural insomnia support. This calculator keeps the SRT protocol consistent while using German country context and dot-separated date display.
Safety Caveats Before You Restrict
Sleep restriction is a clinical behavioural therapy, not a general sleep tip, and it is not appropriate for everyone. Do not start it if you have bipolar disorder, a seizure disorder, untreated obstructive sleep apnoea, or a job or condition where daytime sleepiness is dangerous (driving, operating machinery); pregnancy and significant medical illness also need a clinician’s sign-off first. Never set the window below the safety floor — the calculator’s smallest option is 4 hours 30 minutes, and anything under 5 hours 30 minutes needs explicit acknowledgement and, ideally, supervision. Persistent excessive daytime sleepiness, mood changes or falling asleep while driving are reasons to stop and seek medical advice. This page is an educational planning aid, not a diagnosis or a prescription.
How the Sleep Window Is Stepped
The window is not fixed for the whole treatment — it moves once a week in small steps. Time in bed starts at your average sleep time from the diary, never below the chosen safety floor, and the wake time stays constant. Each week you compute sleep efficiency as total sleep time divided by time in bed: at 85 percent or more the window extends by 15 minutes; below 80 percent it shrinks by 15 minutes; from 80 percent to below 85 percent it holds. Compression mode instead trims 15 minutes a week toward the target, and the gentle-buffer variant keeps a small margin above your average sleep. Adjust on weekly averages, never on a single bad night.
Sources and Methodology
The sleep window method follows standard CBT-I sleep restriction principles: estimate average sleep time from a diary, set a conservative minimum time in bed, then adjust gradually based on sleep efficiency. Use this as an educational planning aid, not as medical advice. Authoritative references include the American Academy of Sleep Medicine, Sleep Foundation CBT-I guidance, and NHS insomnia self-help materials.
Last reviewed: November 2026.
This calculator provides educational information only. It is not a substitute for professional medical advice, diagnosis, or treatment. Sleep restriction therapy can increase daytime sleepiness and may not be suitable for everyone.
Frequently Asked Questions
Is this medical advice?
No. This calculator provides educational estimates based on published SRT protocols. It is not personal medical advice. Stop or choose a gentler setting if daytime sleepiness becomes a problem. Be especially careful with bipolar disorder, seizure disorders, untreated sleep apnea, or safety-critical work.
What if the formula output is below 5.5 hours?
The default safety floor is 5.5 hours. You can adjust this in advanced settings, but lower floors may increase daytime sleepiness and should be used with extra caution.
What is sleep compression?
Sleep compression gradually reduces time in bed over several weeks rather than making an abrupt restriction. The default plan is 6 weeks. Each week is calculated from the difference between your current time in bed and the target.
How often should I recalculate?
SRT is commonly reviewed weekly using the past week of sleep data. After one week at the new window, use Recalculating mode with your new diary and current time in bed.
Can I exclude an unusual night from my diary?
Yes. Use Exclude for nights that were not representative, such as illness, travel, or unusual circumstances. Excluded nights are not counted in the average.
How is threshold bedtime calculated?
Threshold bedtime = your fixed wake time minus the selected sleep window. For example, a 7:00 AM wake time and a 5-hour-45-minute window give a 1:15 AM bedtime.
What is the sleep window formula?
Use your diary’s average total sleep time as the starting window. Standard uses the average; Gentle adds the selected buffer; Compression uses the selected target variant and moves toward it gradually. The selected safety floor is applied, and the result is rounded up to the next 5 minutes.
What does the 300-minute (5-hour) minimum mean?
It means the window will not be shorter than 300 minutes when that floor is selected. The default is 330 minutes (5 hours 30 minutes); 300 and 270 minutes remain configurable, stricter options that call for extra caution and may increase daytime sleepiness.
What does the 85% sleep-efficiency threshold mean?
In weekly recalculation for Standard and Gentle, efficiency at or above 85% extends the window by 15 minutes; below 80% reduces it by 15 minutes only when the window is above the selected floor; from 80% to below 85%, or already at the floor, the window is held. Compression instead follows its gradual week-by-week plan toward the selected target. These are calculator rules, not personal treatment advice.
Related Tools and Guides
Sleep Restriction Therapy Explained
How sleep restriction therapy works for insomnia: time in bed, sleep efficiency, fixed wake time, safety floors, and weekly adjustments.
Sleep Diary and Sleep Efficiency
How to track your sleep with a sleep diary and calculate sleep efficiency for CBT-I sleep restriction therapy.
How to Adjust Your Sleep Window Week by Week
How to adjust your sleep window each week based on sleep efficiency during CBT-I sleep restriction therapy.
Sleep Compression vs Sleep Restriction
The difference between sleep compression and sleep restriction therapy, and when a gradual approach may be more appropriate.
When Sleep Restriction May Not Be Appropriate
Medical and safety considerations before trying sleep restriction therapy: bipolar disorder, seizure risk, sleep apnea, and other contraindications.
CBT-I sleep-window protocol
Sleep restriction therapy: your window, the rules, and a four-week sleep log.
Your sleep window
Bedtime ______ → Wake time ______ · Time in bed ______
Work out the window first, then write the times here.
The rules
- Get up at the same time every day, weekends included.
- Stay inside the window: no sleep and no time in bed outside it, and no naps.
- Awake for around 20 minutes? Get out of bed and go back only when sleepy.
- Fill in one row of the log each morning.
- Review once a week. Efficiency = total sleep ÷ time in bed. 85% or more: 15 minutes earlier. Under 80%: 15 minutes later. 80% to below 85%: keep the window unchanged.
- Never go below the safety minimum (5 h 30 min by default) without a clinician’s advice.
- Do not drive when you are very sleepy. Get medical advice before starting if you have severe daytime sleepiness, bipolar disorder, a seizure disorder, or safety-critical work.
Sleep log — four weeks
One row per night, filled in the morning.
Week 1
| Date | Bedtime | Wake time | Time in bed | Total sleep | Efficiency % |
|---|---|---|---|---|---|
Week average efficiency ______ % → next week: ☐ 15 min earlier ☐ unchanged ☐ 15 min later
Week 2
| Date | Bedtime | Wake time | Time in bed | Total sleep | Efficiency % |
|---|---|---|---|---|---|
Week average efficiency ______ % → next week: ☐ 15 min earlier ☐ unchanged ☐ 15 min later
Week 3
| Date | Bedtime | Wake time | Time in bed | Total sleep | Efficiency % |
|---|---|---|---|---|---|
Week average efficiency ______ % → next week: ☐ 15 min earlier ☐ unchanged ☐ 15 min later
Week 4
| Date | Bedtime | Wake time | Time in bed | Total sleep | Efficiency % |
|---|---|---|---|---|---|
Week average efficiency ______ % → next week: ☐ 15 min earlier ☐ unchanged ☐ 15 min later
Educational use only; this sheet is not medical advice.