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Incident Frequency Rate Calculator

A frequency rate normalises injury counts against exposure so sites of different sizes can be compared fairly.

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How to use this calculator

Enter Values

Enter your values and press Calculate to see results.

How to use this calculator

  1. Enter the total hours worked by everyone on site over the reporting period (month, quarter or year).
  2. Enter the counts of lost-time injuries, medical-treatment injuries and restricted-work cases — leave a box blank if you have none.
  3. Optionally add total days lost to also get a severity rate, then read the LTIFR and TRIFR per million hours worked.

How it works

A frequency rate normalises injury counts against exposure so sites of different sizes can be compared fairly. The standard formula is: frequency rate = number of injuries × 1,000,000 ÷ total hours worked. The 1,000,000 base means the result reads as "injuries per million hours worked". LTIFR counts only lost-time injuries (those causing at least one full day or shift off work); TRIFR counts all recordable cases — lost-time plus medical-treatment plus restricted-work/other recordable cases.

This calculator adds your recordable case types to form the total recordable count, then applies the per-million-hours formula to give both LTIFR and TRIFR. If you enter days lost, it also computes a severity rate (days lost × 1,000,000 ÷ hours). Note that jurisdictions differ: some schemes use a per-200,000-hours or per-100-worker base and define "recordable" differently, so always confirm the base and case definitions your regulator requires before benchmarking.

Worked example

Site with 3 lost-time injuries over 500,000 hours. A site records 3 lost-time injuries (LTIs), 5 medical-treatment injuries and 2 restricted-work cases across 500,000 hours worked for the year. LTIFR = 3 × 1,000,000 ÷ 500,000 = 6.00 per million hours. Total recordable cases = 3 + 5 + 2 = 10, so TRIFR = 10 × 1,000,000 ÷ 500,000 = 20.00 per million hours. With 42 days lost, the severity rate = 42 × 1,000,000 ÷ 500,000 = 84.00 per million hours.

Common mistakes

  • Using hours for only one worker or one week instead of the total hours worked by every worker across the whole reporting period — the hours figure must match the same period as the injury counts.
  • Double-counting a single injury in more than one box (e.g. counting a lost-time injury again as a medical-treatment injury); each case should be classified once at its most serious outcome.
  • Assuming the 1,000,000 base is universal — some schemes (notably US OSHA) use a 200,000-hour base, which gives a different-looking number for the same data.

Frequently asked questions

What is the difference between LTIFR and TRIFR?

LTIFR (lost-time injury frequency rate) counts only injuries that caused at least one day or shift away from work. TRIFR (total recordable injury frequency rate) is broader — it counts lost-time injuries plus medical-treatment and restricted-work cases. TRIFR is therefore always equal to or higher than LTIFR for the same period.

Why multiply by 1,000,000?

Multiplying by 1,000,000 expresses the rate as injuries per million hours worked, a common base used in Australia, the UK and much of the world. It turns a small fraction into a readable number and lets you compare sites of very different sizes. Some schemes use a different base (for example OSHA's 200,000 hours), so check which one your regulator requires before benchmarking against published figures.

Do these rates prove my site is safe or unsafe?

No. Frequency rates are lagging indicators and can swing widely on small sites with few hours worked, where a single injury moves the number a lot. Use them alongside leading indicators (hazard reports, inspections, training) and follow your jurisdiction's WHS/OSH regulations. Treat the output as guidance only, not a compliance determination.

Related tools

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Cite this tool

Zerdly. (2026). Incident Frequency Rate Calculator. Retrieved from https://www.zerdly.com/tools/incident-frequency-rate-calculator/

Tip: Enter any known values to calculate the remaining results.

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