Sleep debt in Titan is the number of hours you slept short of your sleep need on a single night. Each night stands alone, and one setting, the Sleep Debt Threshold, defines your need.
01Sleep need is the Sleep Debt Threshold
Your sleep need is one fixed number of hours. It comes from a single setting called Sleep Debt Threshold. The default is 7.5 hours. You can set it anywhere from 5 to 12 hours in steps of 0.5 hours.
To change it, tap your avatar on Today to open You, tap the gear icon to open Settings, then tap Recovery & Sleep. The Sleep Debt Threshold stepper sits below Sleep Tracker. The value you choose becomes the Need for every night in your history.
02How sleep debt is calculated
Titan compares your time asleep with your need for each night. Time asleep counts only sleep, so awake time in bed does not count toward it. If you slept less than your need, the shortfall is that night's debt. If you slept your need or more, the debt is 0.
| Need | Time asleep | Sleep debt that night |
|---|---|---|
| 7.5 h | 6.0 h | 1.5 h |
| 7.5 h | 7.5 h | 0 h |
| 7.5 h | 9.0 h | 0 h |
A night with no sleep data in Apple Health has no debt value. Titan leaves it blank and does not treat it as 0 or as a full night of debt. See sleep missing if nights you slept are blank.
03Debt is per night and does not accumulate
Each night's debt stands alone. Titan does not carry a shortfall forward and does not keep a running total. Three nights of 1.5 hours short show as three separate bars of 1.5 hours. Titan never shows a combined 4.5 hours.
Extra sleep does not pay anything back either. A 9 hour night after a 6 hour night shows 0 debt for the long night. The 1.5 hours from the short night stays on the short night's bar.
To judge a run of short nights, read the pattern of bars across the week. The latest value covers one night only.
04Where you see sleep debt
On Today, tap the Sleep card to open the Sleep screen.
- The Sleep target section shows Target, which is your sleep goal, and Need, which is your Sleep Debt Threshold.
- The Sleep history section has a Debt tab. It charts nightly debt for 7 Days, 30 Days or 60 Days.
Titan calculates sleep debt for the last 60 days each time Today refreshes. When you change the Sleep Debt Threshold, Titan recalculates the debt history for at least the last 60 days with the new value. Past debt values then reflect your current threshold.
05Sleep goal and Sleep Debt Threshold are separate settings
Titan has two sleep hour settings, and they do different jobs.
Sleep Goal lives in your profile. Tap your avatar on Today, tap your profile card on You, and change Sleep Goal under Daily Targets. The default is 8 hours, with a range of 4 to 12 hours in 0.5 hour steps. The Sleep score uses the Sleep Goal as its duration target, and the Sleep screen shows it as Target.
The Sleep Debt Threshold sets your need and drives sleep debt. It does not change the Sleep score. For the rest of the Sleep score math, see how the Sleep score works.
06Using sleep debt with the Journal
Journal Insights can compare Sleep Debt on tagged days against untagged days. That shows whether a habit such as a late meal or alcohol lines up with nights you fell short of your need. See Journal Insights for how Titan calculates impact.
