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Hndy Tools

Fatigue Risk Calculator

Assess your fatigue level for shift work safety based on sleep and circadian factors

Shift Work
Sleep
Safety
Circadian

Calculate Your Fatigue Risk

Recommended: 7-9 hours

Recommended: 14-18 hours

Risk increases significantly after 16 hours

Circadian low: 2-6 AM

1 = Very poor (frequent waking, not restful) | 10 = Excellent (deep, uninterrupted)

About This Tool

The Fatigue Risk Calculator helps shift workers, drivers, and safety-conscious professionals assess their current fatigue level. It uses a research-backed scoring system that considers five key factors: sleep deficit, hours awake, circadian timing, cumulative sleep debt, and shift type.

Extended wakefulness significantly impairs cognitive performance. Studies show that being awake for 17+ hours produces impairment equivalent to a blood alcohol level of 0.05%, while 24 hours of wakefulness is similar to 0.10% BAC.

For comprehensive sleep tracking, try our Sleep Debt Calculator. To understand how caffeine affects your alertness and sleep, use our Caffeine Half-Life Calculator.

All calculations happen in your browser - no data is sent to any server. Your assessment history is stored locally on your device only.

Frequently Asked Questions (FAQ)

How is fatigue risk calculated?
The calculator uses a composite scoring system based on five research-backed factors: sleep deficit in the last 24-48 hours, hours spent awake, circadian rhythm timing, cumulative sleep debt from consecutive poor sleep days, and shift type. Each factor contributes to an overall fatigue score from 0-100.
What is the circadian low point?
The circadian low point occurs between 2-6 AM when your body naturally wants to sleep. During this window, alertness and performance are at their lowest, making it the highest-risk time for fatigue-related errors and accidents.
How does extended wakefulness affect performance?
Being awake for 17 hours straight produces cognitive impairment equivalent to a blood alcohol level of 0.05%. After 20+ hours awake, impairment is similar to 0.08% BAC - the legal limit for driving in many jurisdictions.
What should shift workers do to manage fatigue?
Shift workers should maintain consistent sleep schedules, use blackout curtains for daytime sleep, take strategic naps before night shifts, limit caffeine to the first half of shifts, and allow recovery time when rotating between shift types. See our Sleep Debt Calculator for tracking sleep patterns.
Is my data stored securely?
All calculations happen in your browser. No data is sent to any server. Your calculation history is stored locally on your device only.
Can caffeine help with fatigue?
Caffeine can temporarily improve alertness, but it cannot replace sleep. Strategic caffeine use (200-400mg) combined with a 20-minute nap can be effective for short-term alertness. Track your caffeine intake with our Caffeine Half-Life Calculator.

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