What is TRIR and how is it calculated?

TRIR is the total recordable incident rate: (number of recordable incidents × 200,000) ÷ total hours worked. The 200,000 represents 100 full-time employees working 40 hours a week for 50 weeks, so the result reads as incidents per 100 workers per year.

What is the difference between TRIR and LTIFR?

TRIR counts all recordable incidents, including those needing only medical treatment. LTIFR counts only injuries that caused lost work time, and is usually expressed per 1,000,000 hours worked. TRIR shows how often things go wrong; LTIFR shows how often they go seriously wrong.

Does ISO 45001 require specific safety metrics?

ISO 45001 does not prescribe a fixed list. Clause 9.1 requires the organisation to determine what must be monitored and measured, and to evaluate OHS performance against it. In practice auditors expect both lagging indicators such as TRIR and LTIFR and leading indicators such as near-miss reporting, inspections and training coverage.

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🦺 Safety & OHS

ISO 45001 Safety Metrics Explained

ISO 45001 does not hand you a list of metrics. Clause 9.1 tells you to decide what to monitor and then evaluate your OHS performance against it — which means the choice, and the defence of that choice, is yours. These are the eleven measures auditors and clients most often expect to see, split into lagging and leading indicators.

📉 Lagging indicators — what already happened

These count harm after the fact. They are the numbers clients and regulators ask for, but on their own they only tell you how last year went.

TRIR — total recordable incident rate
(Recordable incidents × 200,000) ÷ Hours worked
Reads as incidents per 100 full-time workers per year. Your headline safety number.
LTIFR — lost time injury frequency rate
(Lost-time injuries × 1,000,000) ÷ Hours worked
Counts only injuries that stopped someone working. Check the multiplier your country or client uses — 200,000 and 1,000,000 both appear.
Severity rate
(Lost days × 200,000) ÷ Hours worked
Frequency tells you how often; severity tells you how badly. A falling TRIR with a rising severity rate is a warning, not a win.
Days away, restricted or transferred (DART)
(DART cases × 200,000) ÷ Hours worked
Isolates the incidents that changed someone's ability to do their job.
Lost time injury days
Total calendar days lost to workplace injury
The raw capacity cost — useful when converting safety into money for the board.

🛡️ Leading indicators — what prevents the next one

These measure the behaviour that stops incidents. An ISO 45001 audit that finds only lagging indicators usually finds an immature system.

Near-miss reporting rate
Near misses reported ÷ Average headcount
A rising number is usually good news: it means people trust the system enough to report.
Inspections completed on schedule
(Inspections done ÷ Inspections planned) × 100
Evidence of clause 9.1 monitoring actually happening, not just being documented.
Corrective action closure rate
(Actions closed within target ÷ Actions raised) × 100
The single figure auditors most often use to judge whether your system is alive.
Safety training coverage
(Employees with current required training ÷ Employees requiring it) × 100
Track currency, not attendance — expired certification counts as a gap.
Audit score
Points achieved ÷ Points available × 100
Trend it across internal and external audits so improvement is visible between certification cycles.
Toolbox talk / consultation participation
(Workers participating ÷ Workers scheduled) × 100
Clause 5.4 requires worker consultation and participation; this is how you evidence it.

🧾 Worked example: calculating TRIR

A plant with 250 employees records 460,000 hours worked in the year and 6 recordable incidents, 2 of which caused lost time.

1. TRIR = (6 × 200,000) ÷ 460,000 = 2.61 incidents per 100 workers
2. LTIFR = (2 × 1,000,000) ÷ 460,000 = 4.35 per million hours
3. If those 2 injuries cost 34 lost days, severity rate = (34 × 200,000) ÷ 460,000 = 14.8

Use exact hours worked, not headcount multiplied by a standard year — overtime and part-time patterns move the denominator enough to change the story.

❓ Common questions

Does ISO 45001 require specific safety metrics?: No fixed list. Clause 9.1 requires you to determine what needs monitoring and measuring and to evaluate OHS performance against it. Auditors then expect a sensible mix of lagging and leading indicators, consistently calculated.
What is the difference between TRIR and LTIFR?: TRIR counts every recordable incident, including medical-treatment-only cases. LTIFR counts only injuries that caused lost work time. TRIR shows how often things go wrong; LTIFR shows how often they go seriously wrong.
Why does the formula use 200,000?: It represents 100 full-time employees working 40 hours a week for 50 weeks, so the rate reads as incidents per 100 workers per year. Some jurisdictions and clients use 1,000,000 instead — state your multiplier on the report so nobody compares apples with oranges.

Free tool: TRIR, LTIFR & severity rate calculator