Impact Tech Solutions · HSE Calculators
MAN-HOURS / EXPOSURE

Man-Hours / Exposure Hours Calculator

Calculates total hours worked across multiple employee/worker groups — the denominator figure needed for OSHA Form 300A and every incident-rate calculator (TRIR, LTIFR, DART, PSE rate).
OSHA convention: "Hours worked" includes time actually on the job for all employees — salaried, hourly, part-time, seasonal, and supervised temporary/contract workers. It excludes vacation, sick leave, holidays, and other paid time off, even though paid. For salaried employees whose hours aren't individually tracked, a common accepted estimate is 2,000 hours/year (40 hrs/week × 50 weeks), adjusted for known extended absences.
Employee / Worker Groups
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Total Workers (all groups)
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Avg Hours / Worker
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Total Hours Worked

Formula Reference

Group Hours = Number of Workers × Average Hours per Week × Number of Weeks Worked
Total Hours Worked = Σ (Group Hours, across all groups)

Where This Number Is Used

TRIR(Recordable Cases × 200,000) ÷ Total Hours Worked
LTIFR(Lost Time Injuries × Base Hours) ÷ Total Hours Worked
DART Rate(DART Cases × 200,000) ÷ Total Hours Worked
API RP 754 PSE Rate(PSE Count × 200,000 or 1,000,000) ÷ Total Hours Worked
OSHA Form 300AReported directly as "Total hours worked by all employees"
Based on OSHA recordkeeping guidance (29 CFR 1904) for calculating total hours worked. This figure directly drives every incident rate your organization reports — always reconcile against actual payroll records where available, and document your estimation method for any group whose hours are approximated, so it can be explained if questioned during an audit or inspection. For customized calculators tailored to your organization, please contact Impact Tech Solutions.