Accident Incidence Rate (AIR) Calculator; Dropped Object Consequence Online Calculator; ICAM; Lost Time Incident Frequency (LTIF) Calculator; Total Recordable Case Frequency (TRCF) Calculator; Downloads Lost time injury frequency rate (LTIFR) refers to the amount or number of lost time injuries, that is, injuries that occurred in the workplace that resulted in an employee's inability to work the next full work day, which occurred in a given period relative to the total number oh hours worked in the accounting period.In many countries, the figure is typically calculated per 1,000,000 hours worked. Calculating Incidence Rates. Now, to calculate the LTIIR (Lost Time Injury Incidence Rate) which is the number of LTIs per 100 (or whatever figure you want) employees we just substitute the number of employees for the number of hours and multiply the number of LTIs by the standardizing factor which is 100.