Your OSHA incident rate tells owners, GCs, and insurers exactly how many recordable injuries your company experiences relative to hours worked. Calculating it wrong -- or not tracking it at all -- can lock you out of bids, inflate your premiums, and trigger OSHA scrutiny.

This guide walks through the exact calculation, what separates TRIR from DART, how to maintain your OSHA 300 log correctly, and how to run the numbers when your workforce spans multiple projects.

Step 1: Understand the Two Core OSHA Rates

OSHA uses two primary incident rate metrics. Both use the same base formula but count different types of incidents.

TRIR (Total Recordable Incident Rate) counts every OSHA-recordable incident: medical treatment beyond first aid, restricted work, days away from work, job transfers, and fatalities.

DART (Days Away, Restricted, or Transferred) Rate counts only the subset of recordable incidents involving lost workdays, restricted duty, or job transfer. It excludes incidents that required medical treatment but did not result in lost time or restriction.

Both formulas look the same:

Rate = (Number of qualifying incidents x 200,000) / Total hours worked

The difference is which incidents qualify. TRIR counts all recordable incidents. DART counts only the more severe ones.

Step 2: Gather Your Data from the OSHA 300 Log

Every employer with more than 10 employees must maintain an OSHA 300 log (Log of Work-Related Injuries and Illnesses). This is your source data.

The 300 log captures:

Employee name and job title
Date and location of the incident
Description of the injury or illness
Classification: death, days away, restricted work/transfer, or other recordable
Number of days away from work
Number of days on restricted duty

At the end of each calendar year, you compile the 300A summary (Summary of Work-Related Injuries and Illnesses), which totals:

Total number of deaths
Total number of cases with days away from work
Total number of cases with job transfer or restriction
Total number of other recordable cases
Total hours worked by all employees during the year

These four case-count totals plus the total hours worked are all you need to calculate both TRIR and DART.

Step 3: Calculate TRIR

Pull these numbers from your 300A summary:

Deaths: (A)
Cases with days away: (B)
Cases with job transfer or restriction: (C)
Other recordable cases: (D)
Total hours worked: (H)

TRIR = ((A + B + C + D) x 200,000) / H

Worked example: A mechanical contractor's 2025 300A shows:

Deaths: 0
Cases with days away: 2
Cases with transfer/restriction: 3
Other recordable cases: 4
Total hours worked: 680,000

TRIR = ((0 + 2 + 3 + 4) x 200,000) / 680,000 = (9 x 200,000) / 680,000 = 1,800,000 / 680,000 = 2.65

Step 4: Calculate DART Rate

Using the same 300A data, DART only counts categories A, B, and C. It excludes "other recordable cases" (category D).

DART = ((A + B + C) x 200,000) / H

Using the same example:

DART = ((0 + 2 + 3) x 200,000) / 680,000 = (5 x 200,000) / 680,000 = 1,000,000 / 680,000 = 1.47

The gap between TRIR (2.65) and DART (1.47) tells you that 4 of 9 recordable incidents were relatively minor -- they triggered medical treatment beyond first aid but did not result in lost time or restricted duty.

Step 5: Determine What Gets Recorded

The single biggest source of error in OSHA incident rate calculations is incorrect classification. Here is the decision framework.

Is it work-related? The injury or illness must arise from an event or exposure in the work environment. Exceptions exist for voluntary recreational activities, personal grooming, self-inflicted injuries, and common colds/flu.

Does it meet the recording threshold? A work-related injury or illness is recordable if it results in:

Death
Days away from work
Restricted work or job transfer
Medical treatment beyond first aid
Loss of consciousness
A significant injury or illness diagnosed by a physician (fracture, punctured eardrum, chronic irreversible disease)

The first aid exception. If the only treatment provided falls within OSHA's first aid list (bandages, non-prescription medication at non-prescription strength, tetanus shots, wound cleaning, eye patches, finger splints, hot/cold therapy, elastic bandages, non-rigid back belts), the case is not recordable even if a physician provides the treatment.

Recording Decision Flowchart

Question	If Yes	If No
Did the injury/illness occur in the work environment?	Continue to next question	Do not record
Is there an exception (personal task, voluntary recreation, eating, cold/flu)?	Do not record	Continue
Did the employee die?	Record (Column G)	Continue
Were there days away from work?	Record (Column H)	Continue
Was there restricted work or job transfer?	Record (Column I)	Continue
Was treatment beyond OSHA's first aid list provided?	Record (Column J)	Do not record
Was there loss of consciousness?	Record (Column J)	Continue
Was a significant injury diagnosed by a physician?	Record (Column J)	Do not record

Step 6: Track Hours Accurately

Hours worked is the denominator of your rate. Getting it wrong inflates or deflates your TRIR proportionally.

What counts as hours worked:

All hours actually worked, including overtime
Do not include vacation, sick leave, holidays, or other non-work time
Do not include hours worked by independent contractors or temporary workers you do not supervise

Common hour-tracking methods:

Method	Accuracy	Effort	Best For
Certified payroll records	High	Low (already collected)	Companies with payroll integration
Time card aggregation	High	Medium	Hourly workforce with daily time entry
Estimation (employees x 2,000 hrs)	Low	Minimal	Only for very small companies
GPS/badge-in tracking	Highest	Low (automated)	Companies with electronic time systems

For multi-project companies, track hours by project site. This allows you to calculate project-specific incident rates in addition to the company-wide rate.

Step 7: Handle Multi-Project Calculations

Construction companies operate across multiple jobsites simultaneously. You need both company-wide and project-specific rates.

Company-wide TRIR is calculated using total incidents and total hours across all projects. This is the number that goes on prequalification forms.

Project-specific TRIR uses only the incidents and hours logged at a particular project. GCs use this to monitor subcontractor safety performance during a project.

Worked example -- multi-project: A drywall sub works on three projects simultaneously.

Project	Incidents	Hours Worked	Project TRIR
Downtown Office Tower	1	85,000	2.35
Hospital Expansion	0	62,000	0.00
School Renovation	2	41,000	9.76
Company Total	3	188,000	3.19

The company-wide TRIR of 3.19 is what appears on prequalification documents. But the project-level view reveals that one project (school renovation) accounts for most of the risk. The GC on that project might require additional safety measures.

Step 8: Calculate the 3-Year Rolling Average

Most prequalification forms request a 3-year rolling TRIR. This smooths year-to-year variation.

Correct method: Pool all incidents and all hours across 3 years, then calculate once.

3-Year TRIR = (All incidents in 3 years x 200,000) / (All hours in 3 years)

Incorrect method: Calculate annual TRIR for each of the 3 years, then average them. This weights each year equally regardless of hours worked, producing an inaccurate result.

Example:

Year	Incidents	Hours	Annual TRIR
2023	2	150,000	2.67
2024	5	400,000	2.50
2025	1	250,000	0.80

Correct 3-year TRIR = (8 x 200,000) / 800,000 = 2.00

Incorrect average of annual TRIRs = (2.67 + 2.50 + 0.80) / 3 = 1.99

In this example the difference is small, but with more variation in annual hours, the gap widens significantly.

When to Record: Timing Requirements

OSHA requires that recordable incidents be entered on the 300 log within 7 calendar days of learning that the incident occurred. Late recording does not change the TRIR calculation (the incident still counts in the year it occurred), but consistent late recording can trigger OSHA citations during inspections.

The 300A summary must be posted in the workplace from February 1 through April 30 each year. Electronic submission via OSHA's Injury Tracking Application (ITA) is required for establishments with 250+ employees and for establishments with 20-249 employees in designated high-hazard industries (construction is included).

FAQs

What is the OSHA incident rate formula? The formula is: (Number of recordable incidents x 200,000) / Total hours worked. The 200,000 multiplier normalizes the rate to 100 full-time workers. This formula applies to both TRIR (all recordable incidents) and DART (only incidents with days away, restriction, or transfer). Use data from your OSHA 300 log and 300A annual summary for the calculation.

Do I include subcontractor hours when calculating my OSHA incident rate? No. Each employer calculates their own rate using only their employees' incidents and hours. As a GC, you calculate your rate using your direct-hire employees only. Each subcontractor calculates their own rate separately. However, GCs do collect and verify sub TRIR data as part of prequalification.

How do I handle an incident that occurs late in the year but results in lost time the following year? The incident is recorded in the year it occurred, not the year the lost time begins. If a worker is injured on December 28, 2025, and begins missing work on January 2, 2026, the recordable case goes on the 2025 log. The days-away count continues into 2026 and updates the 2025 log accordingly. Cap the days-away count at 180 days.

Is a workplace injury at a subcontractor's shop recorded on the project OSHA log? No. The OSHA 300 log is maintained by establishment. If a sub fabricates materials at their own shop and a worker is injured there, that incident goes on the sub's log for their shop establishment, not the project log. Only incidents occurring at the project site go on the project log.

What happens if I discover a recordable incident was not recorded? Add it to the log immediately. OSHA allows corrections to the 300 log throughout the 5-year retention period. Recalculate your TRIR for the affected year and update any prequalification submissions that relied on the incorrect number. Not recording a recordable incident is itself an OSHA violation (29 CFR 1904.29).

Can I exclude COVID-19 cases from my OSHA incident rate? COVID-19 cases are recordable if the illness is work-related, confirmed by a test, and meets recording criteria. OSHA's enforcement guidance on COVID-19 recording evolved throughout 2020-2023. As of 2024, standard recording criteria apply with no special COVID exemptions. If a work-related COVID case resulted in medical treatment beyond first aid, restriction, days away, or death, it counts toward your TRIR.

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