Sleep Diary and Sleep Efficiency

What a Sleep Diary Tracks

A standard CBT-I sleep diary records six pieces of information per night. The wake-up date (the date you woke up, not the date you went to bed) serves as the row identifier. Bedtime is the time you got into bed intending to sleep. Sleep onset latency is your estimate of how long it took to fall asleep after getting into bed. Wake time is your final morning awakening. Out-of-bed time is when you actually got up. Nighttime awakenings include the number of awakenings and their total duration.

From these inputs, two derived values are calculated. Time in bed (TIB) is the interval between bedtime and out-of-bed time. Total sleep time (TST) is TIB minus sleep onset latency minus total time awake during the night. Sleep efficiency is TST divided by TIB, expressed as a percentage. Most CBT-I protocols also compute a weekly average of TST and sleep efficiency across valid diary nights.

• Consistency matters: record entries each morning, not later from memory.
• Use the wake-up date for each row — a single night spans two calendar dates.
• Include weekend nights; insomnia patterns often differ on non-work days.

How to Calculate Sleep Efficiency

Sleep efficiency is a straightforward formula but is easily miscalculated if you confuse TIB with TST. Suppose you go to bed at 11:00 PM, fall asleep around 12:00 AM, wake at 6:00 AM, and get up at 6:30 AM. Your TIB is 7.5 hours (450 minutes), from 11:00 PM to 6:30 AM. Your TST is 6 hours (360 minutes), from 12:00 AM to 6:00 AM — subtracting both the 60-minute sleep onset latency and any wakeful periods. Sleep efficiency = (360 / 450) x 100 = 80%.

The same calculation repeated across 7 nights produces a weekly average efficiency. This percentage is the single most important metric in CBT-I. It determines whether your sleep window expands, stays the same, or contracts. The 85% threshold is not arbitrary: studies of good sleepers consistently show efficiency above 85%, while insomnia patients typically fall below 80%.

You can compute efficiency manually with a calculator or let the Sleep Restriction Therapy Calculator handle it automatically. The built-in diary tool on this site records each night's data and computes the weekly averages with the adjustment decision built in.

Minimum Data Requirements and Common Pitfalls

The AASM clinical practice guideline and most structured CBT-I protocols recommend a minimum of 7 consecutive nights of diary data before calculating the initial sleep window. Some programs prefer 10-14 nights for a more reliable baseline. Fewer than 5 nights produces an average that may swing considerably with a single outlier.

Common tracking errors include estimating TIB as TST (overestimating sleep), recording bedtime as the time you got into bed but discounting the time spent reading or watching before lights-out, and forgetting to account for long middle-of-the-night awakenings. The 20-minute rule applies to wake-after-sleep-onset (WASO): many people underestimate how long they were awake during the night. A clock check or a simple bedside log can improve accuracy.

Occasional poor nights due to illness, travel, or unusual stress can be excluded from the weekly average. Mark these nights as exceptions rather than hiding the data. Most CBT-I calculators include a toggle to include or exclude a given night from the calculation.

How the SRT Calculator Uses Diary Data

The Sleep Restriction Therapy Calculator on this site integrates the sleep diary directly into the therapy workflow. You enter each night's data into the built-in diary table, and the calculator automatically computes your average TST, average TIB, and weekly sleep efficiency. From these averages, it proposes an initial sleep window.

After the first week, the calculator applies the standard three-tier rule: extend by 15 minutes at 85% or higher, hold at 80-85%, or restrict by 15 minutes below 80%. The adjustment is applied to your bedtime while the fixed wake time remains unchanged. The calculator tracks your progress week by week and displays the history so you can see how efficiency changes as the window adjusts.

This integration eliminates the busywork of manual calculation and reduces the risk of arithmetic errors that could lead to incorrect window adjustments.

Digital vs Paper Tracking

Paper sleep diaries remain the gold standard in clinical research because they capture subjective experience and do not require a device. The NIH-funded Consensus Sleep Diary (CSD) is a validated paper template used in hundreds of studies. The VA CBT-I Coach app offers a structured digital alternative with built-in reminders and automatic efficiency calculation.

Wearable trackers (smartwatches, rings, mattress sensors) add convenience but introduce two problems for CBT-I: they estimate sleep using movement and heart rate rather than asking whether you were actually asleep, and they lack the subjective component (anxiety before sleep, frustration during awakenings). The AASM guideline notes that actigraphy may complement but should not replace a subjective diary for CBT-I. A practical approach is to use a wearable for general patterns and a diary for the precise numbers that drive weekly adjustments.

The Sleep Restriction Therapy Calculator includes a built-in sleep diary that automatically calculates TIB, TST, and sleep efficiency for each night and across the full treatment cycle. By directly integrating the diary with the weekly adjustment algorithm, the calculator eliminates manual calculations and reduces the risk of arithmetic errors, especially when adjusting the sleep window after a week of variable sleep patterns.

Reading Your Device's Numbers

An app, a smartwatch or a ring gives you several numbers at once, and they are not all worth acting on. The useful ones are the numbers that map onto a decision this page has already set out.

• Sleep efficiency: when the device reports a weekly efficiency, compare it against the 85% target. The Sleep Restriction Therapy Calculator keeps that diary for you and applies the weekly adjustment to the sleep window, so the number becomes a change to your bedtime rather than a score to watch.
• “Sleep debt” or a recovery deficit: the shortfall your app shows is the input the Sleep Debt Calculator prices — your sleep need, an average night, and a window of 7 or 14 nights — turning it into a total and an estimate of how long recovery may take at the pace you choose.
• Sleep stages: the device infers them from movement and heart rate rather than from brain activity, so read the stage breakdown as a pattern across nights and not as a measurement of one night; only EEG can measure true sleep stages.
• A readiness or recovery score: worth watching as a trend, but it is derived from the same signals and cannot stand in for the diary when the 85% decision is made each week.

Where to Go Next

With a week of nights recorded, the numbers decide what happens next: How to Adjust Your Sleep Window Week by Week explains what an efficiency at or above 85 percent, below 80 percent or in between means for your window, week by week.