The general-purpose BLS (Bureau of Labor Statistics) incidence rate formula — the same underlying calculation used for TRIR, DART, and DAFW rates, applicable to any case category on your OSHA Form 300A.
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INCIDENCE RATE
Formula Reference
Incidence Rate = (Number of Cases × Multiplier) ÷ Total Hours Worked
Injury / combined categories
200,000 base — rate per 100 full-time workers
Illness-only subcategories
20,000,000 base — rate per 10,000 full-time workers
Per BLS guidance, when comparing illness rates specifically by type (skin disorders, respiratory conditions, hearing loss, etc.), use the 20,000,000-hour base instead of 200,000 — this produces a rate per 10,000 equivalent full-time workers rather than per 100, since illness-specific case counts are typically much smaller and a per-100 rate would be too coarse to be meaningful.
Where to Find Your Case Counts (OSHA Form 300A)
Total Recordable
Column H + Column I + Column J
DAFW
Column H
Restricted/Transfer
Column I
Other Recordable
Column J
Illness subcategories
Columns M-1 through M-6
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