How do you calculate a fatigue risk score?

Rate severity, occurrence and detection each 1-10, then weight: severity x 0.40 + occurrence x 0.35 + detection x 0.25. Severity 8, occurrence 6 and detection 7 give 8x0.40 + 6x0.35 + 7x0.25 = 7.05.

What is a good fatigue risk score?

Lower is better. Below 3 is generally acceptable, 3 to 6 warrants monitoring and scheduled breaks, and 7 or higher (like the 7.05 example) signals a shift or task that needs active countermeasures now.

Why weight severity over occurrence and detection?

Severity gets 0.40 because a fatigue error on a high-consequence task, such as operating a crane or press, matters most even if fatigue is occasional. Detection gets only 0.25 because visible drowsiness or buddy checks make some risk containable.

Fatigue Risk Score vs a fatigue management system, what is the difference?

A full fatigue risk management system uses schedules, sleep data, and biomathematical models. This score is a quick triage that tells you which shifts and tasks to feed into that deeper process first.

How do 12-hour and night shifts affect the score?

They typically raise the occurrence factor because fatigue accumulates faster, and often raise severity if the work is high-consequence, pushing the weighted score into the action band.

How often should we reassess fatigue risk?

Reassess whenever you change shift length, rotation direction, overtime levels, or staffing, and after any near-miss where tiredness was a factor, since each of those shifts the occurrence and severity inputs.

Safety & Workforce calculator

Fatigue Risk Score Calculator

The Fatigue Risk Score gives EHS managers and shift planners a repeatable way to grade how dangerous fatigue is for a given task or shift pattern. It borrows FMEA logic, weighting how severe a fatigue-driven error would be, how often fatigue actually builds up under that schedule, and how hard tiredness is to spot before it causes a slip. Manufacturers running rotating shifts, long overtime stretches, or night operations use it to decide where to add breaks, staffing, or monitoring. The single number makes it easy to compare a 12-hour night crew against a standard day line.

What this calculator does

Score fatigue risk from overtime, shift length, and rotation factors.
Use it when fatigue risk in safety and workforce needs a defensible ranking against other safety and workforce risks for the next review.
It computes a weighted fatigue risk score for one task or shift by blending error severity (0.40), how often fatigue occurs (0.35), and how detectable fatigue is before an error (0.25).

Formula used

Weighted score = severity × 0.40 + occurrence × 0.35 + detection × 0.25

Inputs explained

Severity of harm if a fatigued worker errs (1-10):
How often fatigue conditions occur on this shift (1-10):
How hard fatigue is to detect before an error (1-10):

How to use the result

Use it when reviewing shift schedules, overtime policy, or high-consequence night work and you need to rank which situations warrant fatigue countermeasures.
It is a subjective risk ranking, not a physiological measurement; it does not replace hours-of-service data, sleep studies, or biomathematical fatigue models for regulated operations.

Current U.S. benchmarks

Manufacturing hourly earnings average $30.27 (BLS, Jun 2026), up 4.4% from a year earlier. Median machinist pay is $28.24/hr (OEWS 2025), with state medians on each state page. Manufacturers have 529k open positions nationally (BLS JOLTS).

Common questions

How do you calculate a fatigue risk score? Rate severity, occurrence and detection each 1-10, then weight: severity x 0.40 + occurrence x 0.35 + detection x 0.25. Severity 8, occurrence 6 and detection 7 give 8x0.40 + 6x0.35 + 7x0.25 = 7.05.
What is a good fatigue risk score? Lower is better. Below 3 is generally acceptable, 3 to 6 warrants monitoring and scheduled breaks, and 7 or higher (like the 7.05 example) signals a shift or task that needs active countermeasures now.
Why weight severity over occurrence and detection? Severity gets 0.40 because a fatigue error on a high-consequence task, such as operating a crane or press, matters most even if fatigue is occasional. Detection gets only 0.25 because visible drowsiness or buddy checks make some risk containable.
Fatigue Risk Score vs a fatigue management system, what is the difference? A full fatigue risk management system uses schedules, sleep data, and biomathematical models. This score is a quick triage that tells you which shifts and tasks to feed into that deeper process first.
How do 12-hour and night shifts affect the score? They typically raise the occurrence factor because fatigue accumulates faster, and often raise severity if the work is high-consequence, pushing the weighted score into the action band.

Last reviewed 2026-05-12.