Lost time injury rate (LTIR) is a measure of qualifying lost-time injuries relative to hours worked using an explicitly stated normalization basis. It is calculated as qualifying lost-time injuries multiplied by a stated normalization factor and divided by hours worked for the same workforce and period. Reporting schemes can use different bases, including 200,000 or 1,000,000 hours; IOGP reports LTIR per million hours.
LTIR and LTIFR can describe the same frequency measure when their definitions and normalization bases match. Their labels alone do not establish a fixed mathematical difference. A report should state the injury criteria, workforce scope, period, and hour basis, and should distinguish the rate from the count of injuries and number of lost days.