How to calculate TRIR (with worked examples)

The practical answer

The arithmetic takes ten seconds. Getting the two inputs right is the part that goes wrong, and a wrong input produces a number you then have to defend to a client for a year.

The formula and the two inputs

TRIR = (recordable incidents × 200,000) ÷ hours worked.

Input one: recordable incidents for the calendar year, taken from your OSHA 300 log — not your insurance claim count, which is a different and usually larger number. Input two: total hours actually worked by all employees that year, from payroll.

Worked examples

A 40-person electrical contractor: 2 recordables, 78,000 hours worked. (2 × 200,000) ÷ 78,000 = 5.13.

A 220-person mechanical contractor: 6 recordables, 430,000 hours. (6 × 200,000) ÷ 430,000 = 2.79.

The larger firm had three times the incidents and roughly half the rate. That inversion is the entire point of the normalization, and it is why raw incident counts are never compared directly.

The mistakes that distort it

Five recur constantly, roughly in order of frequency:

• Using scheduled hours instead of hours worked — overtime in, vacation and holiday out. Padding the denominator understates the rate and is the version most likely to be audited.
• Counting first-aid-only cases as recordable. The OSHA first-aid list is exhaustive and narrower than intuition; treatment beyond it is recordable, treatment on it is not.
• Including subcontractor or temp-agency hours you don't supervise — or excluding temp workers you do direct, whose injuries generally belong on your log.
• Mixing a fiscal year into a calendar-year metric. The 300A is calendar-year.
• Carrying a corrected incident count on the 300A but never recomputing the rate you submitted.

Which years to submit

Almost every client asks for three years, and they read the trend as much as the level. A contractor moving 6.1 → 4.4 → 3.0 is telling a better story than one flat at 3.0, and a far better one than 2.1 → 3.4 → 5.0 even though that contractor's best year was the strongest number on the page.

Submit the three years as filed, with hours worked shown alongside. A rate without its denominator invites the question anyway, and volunteering it reads as confidence rather than as an excuse.

Calculating DART alongside it

Same denominator, narrower numerator: DART = (incidents involving days away, restricted work or transfer × 200,000) ÷ hours worked. DART is always at or below TRIR. A DART close to TRIR means most of your recordables were serious; a low DART against a higher TRIR means they were mostly minor.

Clients read the pair together. Compute both from the same 300A in one pass.

Doing it once, correctly, for a whole sub list

If you are the hiring party, you are not calculating your own rate — you are re-calculating thirty subcontractors' rates from thirty differently-formatted 300A summaries, and taking their word for it is how a bad number enters your file.

CoverWarden computes TRIR and DART from the uploaded 300A automatically, checks the EMR letter against the cap you set, and flags where a submitted figure disagrees with the underlying log. The sub uploads through a free no-login link; the arithmetic stops being your problem.