Sleep Debt & Fatigue Logger
Log actual sleep against your personal requirement across a rolling shift block, and watch your accumulated sleep debt and projected fatigue level, before it becomes a safety problem.
Accumulated sleep debt
7.5h
Red band
Performance is comparable to alcohol impairment. Treat driving with real caution, avoid safety-critical extras, and make your next off-day a managed recovery day.
Premium members can save rolling blocks and see historical fatigue trends. Data currently stays in your browser.
Why this matters on a real rota
Sleep debt is sneaky. One short sleep feels fine. Three short sleeps in a 4-on block and your reaction time is legally-drunk equivalent, and you're the last person able to judge it, because impairment blunts self-assessment first.
This logger tracks the gap between the sleep you need and the sleep you actually got across your current shift block, then translates the accumulated debt into a plain-English fatigue banding used across safety-critical industries.
On the landings, on the line, behind the wheel of a forklift at 5am, the workers who last decades are the ones who treat sleep debt like an overdraft: fine to dip into, dangerous to live in.
How the calculator works
Set your personal nightly requirement (most adults: 7–9 hours).
Log the actual hours you slept for each day of your current block.
The logger sums your rolling debt and assigns a fatigue band: Green (under 2h), Amber (2–5h), Red (5–8h), Critical (over 8h).
Each band comes with a practical action, from 'protect tonight's sleep' to 'do not drive; recovery sleep is now a safety requirement'.
Frequently asked questions
What is sleep debt?
Sleep debt is the running total of the difference between the sleep your body needs and the sleep it actually gets. Need 8 hours and get 5.5 across four nights? You're carrying 10 hours of debt, comparable to missing an entire night.
How much sleep debt is dangerous?
Performance measurably degrades from about 2 hours of accumulated debt. Beyond 5 hours in a rolling week, reaction time and judgement decline to levels comparable with alcohol impairment. Over 8 hours, driving and safety-critical work carry serious risk.
Can you pay back sleep debt with a lie-in?
Partially. A single long sleep recovers alertness faster than it recovers accuracy and judgement, those take two to three nights of solid sleep. That's why the smart play is stopping the debt building mid-block, not banking on one heroic day-off sleep.
How much sleep do shift workers actually need?
The same 7–9 hours as everyone else, the difference is shift workers rarely get it in one block. Counting a main sleep plus a planned nap toward your daily total is a legitimate and often necessary strategy on rotating rotas.
FIELD tools are lifestyle and operational-safety aids for shift workers, built from real-world experience. They are not medical devices or diagnostic tools. If fatigue or sleep problems are affecting your health, speak to your GP.