TRIR calculator: free TRIR calculation, LTIFR formula and worked example

Lost time injuries

Injuries that keep a person off work beyond the day or shift on which the accident happened. See the note below.

1,000,000

The per million hours basis used in India under IS 3786 and in most of the world.

Hours worked

Total hours actually worked by everyone on the premises in the period, including overtime. IS 3786 includes contract labor.

The calculator can also show LTIFR on the 200,000 hour basis, to line it up with TRIR. The same injuries give a figure five times smaller on that basis, so always state which one you use.

Recordable cases

Work-related injuries and illnesses that meet the recording criteria. See the note below.

200,000

The OSHA basis: 100 full-time workers at 40 hours a week for 50 weeks a year.

Hours worked

The same total hours actually worked. Leave out paid time off such as leave and holidays.

Lost time injury. IS 3786 from the Bureau of Indian Standards defines a disabling injury, or lost time injury, as one causing disablement that extends beyond the day or shift on which the accident occurred. An injury that needs only medical treatment, with no disablement, is a non-disabling injury and does not count.

Recordable case. Under OSHA's rule 29 CFR 1904.7, a work-related injury or illness is recordable if it results in any of these:

• death
• days away from work
• restricted work or transfer to another job
• medical treatment beyond first aid
• loss of consciousness
• a significant injury or illness diagnosed by a physician or other licensed health care professional

So every lost time injury is also a recordable case, but many recordable cases, such as a cut that needs stitches and no time off, are not lost time injuries. That is why TRIR is usually higher than LTIFR on the same basis.

Both rates are frequencies. They tell you how often people get hurt, not how badly. One lost time injury of two days and one of two months count the same.

Compare a rate only with another rate on the same basis and the same rules for hours and contractors. Your own trend, quarter on quarter, is the most honest comparison. At a small site, one case moves the rate a lot, so look at several periods before you draw a conclusion.

A falling rate is good news only if reporting is still honest. If near misses and first aid cases dry up at the same time, ask why.

Most errors come from the basis or the hours, not the multiplication.

• Mixing the 200,000 and 1,000,000 bases. An LTIFR per million hours compared with one per 200,000 hours makes one site look five times worse.
• Using headcount times a standard week. Use hours actually worked from attendance or time records. Estimates overstate hours when people are on leave.
• Counting paid leave as hours worked. Leave and holidays are not exposure hours.
• Leaving out contractors on one side only. If contractor hours are in, contractor cases must be in too. IS 3786 counts contract labor in man-hours worked.
• Counting first aid cases as recordable. First aid alone does not make a case recordable.

Your EHS head reports LTIFR and TRIR without a separate spreadsheet. The MaintenanceIQ EHS module keeps a man-hours register next to the incident register, and the rates are worked out from them each time you view them, so a corrected entry never disagrees with its own total. See the EHS module.

• IS 3786:1983, Methods for computation of frequency and severity rates for industrial injuries and classification of industrial accidents (opens in a new tab), Bureau of Indian Standards (copy hosted by Public.Resource.Org). The lost time injury definition, the per 1,000,000 man-hours frequency rate and what man-hours worked include.
• 29 CFR 1904.7, General recording criteria (opens in a new tab), US Code of Federal Regulations (Legal Information Institute). What makes a work injury or illness recordable.
• How to compute a firm's incidence rate for safety management (opens in a new tab), US Bureau of Labor Statistics. The 200,000 hour formula and which hours to leave out.