The incident rate formula OSHA uses is deceptively simple. Multiply the number of recordable incidents by 200,000, then divide by total hours worked. But getting the inputs right requires precision that most GCs underestimate.

Wrong inputs produce wrong rates. Wrong rates produce wrong prequalification answers. Wrong prequalification answers cost you contracts.

This guide breaks down every component of the OSHA incident rate formula, shows you where errors hide, and recommends the tools that keep your calculations audit-proof.

The OSHA Incident Rate Formula Explained

OSHA uses a standardized formula to calculate workplace injury and illness rates. The formula normalizes incident data to a common base, allowing comparisons across companies of different sizes.

The formula:

Incident Rate = (Number of Recordable Cases x 200,000) / Total Hours Worked

What each component means:

Number of Recordable Cases: OSHA-recordable injuries and illnesses as defined by 29 CFR 1904. This includes any work-related injury or illness that results in death, days away from work, restricted work, transfer to another job, medical treatment beyond first aid, loss of consciousness, or diagnosis of a significant condition.
200,000: Represents the equivalent of 100 full-time workers working 40 hours per week for 50 weeks. This constant standardizes the rate across organizations of all sizes.
Total Hours Worked: Actual hours worked by all employees during the measurement period. This includes overtime but excludes vacation, sick leave, and other non-work hours.

Example calculation:

Input	Value
Recordable incidents in 2025	7
Total hours worked in 2025	485,000
Calculation	(7 x 200,000) / 485,000
Incident rate (TRIR)	2.89

This GC's TRIR of 2.89 sits slightly above the construction industry average of 2.8, placing them at a competitive disadvantage in prequalification.

Getting the Numerator Right: What Counts as Recordable

The most common calculation errors start with miscounting recordable cases.

Recordable incidents include:

Any work-related fatality
Any injury requiring days away from work
Any injury requiring restricted work duties or job transfer
Any injury requiring medical treatment beyond first aid
Loss of consciousness from any work-related cause
Significant injuries or illnesses diagnosed by a physician (e.g., fractures, punctured eardrums, chronic conditions)

First aid treatments that are NOT recordable:

Bandages, butterfly closures, or wound closure strips
Tetanus shots (when given as preventive measure)
Eye flushing for foreign body removal
Non-prescription medications at nonprescription strength
Drilling of fingernails or toenails to relieve pressure
Hot or cold therapy
Temporary splints or slings used during transport

The gray areas that trip up GCs:

Stitches vs. butterfly closures. Stitches are medical treatment (recordable). Butterfly closures are first aid (not recordable). The treating physician's choice of wound closure method determines recordability.
Prescription medications. Any prescription medication makes the case recordable, even a single dose of prescription-strength ibuprofen.
Physical therapy. Treatment by a physical therapist is medical treatment. The case becomes recordable the moment PT is prescribed, regardless of the injury's apparent severity.
Diagnostic procedures. X-rays, MRIs, and other diagnostics alone do not make a case recordable. Recordability depends on the treatment prescribed based on the diagnostic findings.

Getting the Denominator Right: Counting Hours Worked

Errors in hours worked calculations distort your incident rate in both directions.

Hours that count:

Regular hours worked
Overtime hours worked
Hours worked by temporary and seasonal employees on your payroll
Hours worked during training (when on the clock)

Hours that do NOT count:

Paid vacation and holiday hours
Sick leave hours
Other paid time off (jury duty, bereavement)
Hours worked by independent contractors (they report under their own OSHA log)
Volunteer hours

Estimation methods when exact hours are unavailable: OSHA allows estimation using average hours per employee. Multiply the number of employees by 2,000 (standard annual full-time hours) for a rough estimate. For more accuracy, adjust by actual overtime percentages and part-time employee ratios.

Use our TRIR Calculator to plug in your numbers and get instant results.

Variations of the OSHA Incident Rate Formula

The base formula calculates TRIR. OSHA and prequalification platforms also use variations that measure severity and specific injury types.

DART Rate (Days Away, Restricted, or Transferred):

DART Rate = (DART Cases x 200,000) / Total Hours Worked

DART cases are a subset of recordable cases. They include only incidents that result in days away from work, restricted duty, or job transfer. DART is a severity measure: a high TRIR with a low DART indicates many minor injuries; a high DART relative to TRIR indicates more serious injuries.

DAFWII Rate (Days Away From Work Injury and Illness):

DAFWII = (Cases with Days Away x 200,000) / Total Hours Worked

Even more specific than DART. Counts only cases where the worker missed at least one full day of work.

Fatality Rate:

Fatality Rate = (Fatalities x 200,000) / Total Hours Worked

Used primarily for industry benchmarking and regulatory reporting.

Rate Type	What It Measures	Prequalification Use
TRIR	All recordable incidents	Primary metric for most owners
DART	Lost time + restricted duty incidents	Required by many prequalification platforms
DAFWII	Lost time incidents only	Severity indicator
Fatality Rate	Fatal incidents	Critical for high-risk project owners

Tools for Calculating and Tracking OSHA Incident Rates

Manual calculations work for annual reporting. Ongoing compliance requires automated tools.

Spreadsheet-based tracking. Adequate for small GCs with fewer than 50 employees. Build a template that captures each incident, automatically calculates running TRIR and DART rates, and flags when you approach owner thresholds. Limitations: no automated alerts, manual data entry errors, and no audit trail.

OSHA recordkeeping software. Purpose-built platforms like iAuditor, Intelex, or SafetyCulture automate incident logging, calculate rates in real time, and generate OSHA 300/300A/301 forms. Cost: $50-$200 per month for small to mid-size firms.

Integrated compliance platforms. Systems that combine OSHA recordkeeping with prequalification, insurance tracking, and subcontractor management. These platforms calculate your rates and automatically populate prequalification questionnaires with current data.

The experience modification rate connection: Your incident rate data feeds directly into EMR calculations performed by your workers' compensation carrier. Accurate incident tracking ensures your EMR reflects actual performance rather than data errors.

Frequently Asked Questions

What is the 200,000 number in the OSHA incident rate formula? The 200,000 represents the total hours 100 full-time employees would work in one year (100 workers x 40 hours/week x 50 weeks). This constant normalizes incident rates so companies of different sizes can be compared on equal footing. A rate of 2.0 means 2 recordable incidents per 100 full-time worker years.

How do I calculate OSHA incident rates for a single project? Use the same formula but limit the inputs to that specific project. Count only recordable incidents that occurred on that project and only hours worked on that project. Project-level rates help identify which jobsites drive your overall company rate higher.

Should I include subcontractor hours and incidents in my calculation? For your company OSHA 300 log and company TRIR, include only your direct employees. However, many owner prequalification programs ask for project-level rates that include all contractors. Track both company-level and project-level data separately to satisfy both requirements.

What is a good incident rate for construction? The BLS construction industry average is approximately 2.8. Top-performing GCs maintain rates between 0.5 and 1.5. Most owner prequalification programs set maximum thresholds at or below the industry average. A rate below 1.5 places you in the top quartile nationally.

How far back should I calculate my incident rate? Most prequalification platforms request your three-year rolling average. Calculate rates for the most recent complete calendar year and the two preceding years. Some owners also request a five-year history. Maintain accurate records for at least five years to satisfy any request.

Can I exclude incidents that were not my company's fault? No. OSHA recordability depends on whether the injury was work-related, not on fault or blame. If a worker sustained a recordable injury during work activities, it goes on your log regardless of circumstances. The only exceptions are the specific exemptions listed in 29 CFR 1904.5(b)(2).

Automate Your OSHA Incident Rate Calculations

Running the OSHA incident rate formula manually once a year is manageable. Keeping it current for rolling prequalification submissions, insurance renewals, and owner audits is not.

SubcontractorAudit calculates your TRIR, DART, and related rates automatically using your incident and hours data. Prequalification forms populate with current numbers. No manual math. No outdated spreadsheets.

Request a demo to see how GCs automate OSHA incident rate calculations.