How LTIFR works
LTIFR normalizes lost-time incidents against hours worked so periods or operations of different size can be compared on the same reporting base.
LTIFR = (lost-time incidents × reporting base) ÷ total hours worked
The result is a frequency rate. It does not measure injury severity and it does not, by itself, explain why incidents occurred.
Worked example
A 20-person shop records one lost-time incident and approximately 40,000 total hours worked during the year.
Lost-time incidents1
Total hours40,000
Base1,000,000
LTIFR25.0
On a 200,000-hour base, the same underlying experience would be reported as 5.0. The event history did not change; only the normalization base did.
Before comparing LTIFR
- BASEConfirm whether your reporting framework uses 1,000,000 or 200,000 hours. Rates using different bases are not directly comparable until converted.
- CASEUse a consistent definition of “lost-time incident.” Organizations and jurisdictions can classify cases differently.
- HOURSUse actual total hours worked for the population covered by the incident count. Keep employee and contractor scope consistent.
- SIZEIn a small shop, one incident can produce a high rate because relatively few hours sit in the denominator. Read the rate together with the underlying incident count.
Reporting note: This calculator performs the arithmetic only. It does not determine which incidents your regulator, insurer, customer or corporate reporting framework requires you to include.