The Lost Time Incident Rate (LTIR) is calculated using a simple formula: multiply the number of lost time injuries by 200,000, then divide by the total hours worked by all employees. The result tells you how many lost time injuries occurred per 100 full-time workers over a year. It’s the standard metric companies use to measure the severity of workplace injuries, and it directly affects insurance premiums, contract eligibility, and regulatory scrutiny.
The LTIR Formula
OSHA’s formula for calculating incidence rates is:
(Number of lost time injuries × 200,000) ÷ Total employee hours worked = LTIR
The 200,000 multiplier represents the total hours 100 employees would work in a year (40 hours per week, 50 weeks per year). This standardizes the rate so you can compare companies of wildly different sizes on equal footing. A 50-person landscaping company and a 10,000-person manufacturer both express their LTIR per 100 full-time equivalent workers.
Here’s a quick example. Say your company had 3 lost time injuries last year, and your employees worked a combined 500,000 hours. The math: (3 × 200,000) ÷ 500,000 = 1.2. That means for every 100 full-time workers, you had 1.2 lost time injuries over the year.
What Counts as a Lost Time Injury
Not every workplace injury qualifies. A lost time injury specifically involves one or more days away from work. The day of the injury itself doesn’t count. You start counting on the day after the injury occurred or the illness began, and you include every calendar day the employee couldn’t work, including weekends, holidays, and vacation days they would have missed due to the injury.
An important nuance: even if the injured employee ignores their doctor’s recommendation to stay home, you still record the days away that the physician recommended. The recording obligation follows the medical recommendation, not what the worker actually does. OSHA caps the count at 180 calendar days per case, so injuries requiring longer recovery don’t skew your numbers indefinitely.
This is a narrower category than a “recordable” incident. OSHA considers an injury recordable if it results in death, days away from work, restricted work or job transfer, medical treatment beyond first aid, loss of consciousness, or a significant diagnosis from a licensed health care professional. Lost time injuries are a subset: only those resulting in actual days away from work.
How to Calculate Total Hours Worked
The denominator in the formula is total employee hours worked during the period you’re measuring, typically a calendar year. This should reflect actual hours on the job. Include regular hours and overtime hours. Do not include paid time off, vacation, sick leave, or holidays where employees weren’t working.
If you don’t track hours precisely (common for salaried employees), you can estimate. A standard full-time employee works roughly 2,000 hours per year. Multiply the number of full-time equivalent employees by 2,000 to get a reasonable estimate. For part-time employees, use their actual scheduled hours. The more accurate your hours data, the more meaningful your LTIR will be.
LTIR vs. TRIR
These two rates use the same formula but count different things. The Total Recordable Incident Rate (TRIR) includes all recordable injuries and illnesses: days away from work, restricted duty, job transfers, and medical treatment beyond first aid. LTIR only counts the subset involving days away from work.
Think of TRIR as measuring how often injuries happen at all, while LTIR measures how often injuries are serious enough to keep someone home. A company could have a moderate TRIR but a low LTIR, meaning injuries occur but are mostly minor. The reverse pattern, where LTIR is high relative to TRIR, signals that when injuries happen, they tend to be severe.
What Your Score Means
The Bureau of Labor Statistics publishes national benchmarks for days-away-from-work rates per 100 full-time workers, using the same 200,000-hour formula. The 2024 national average across all industries is 1.5. Here’s how specific sectors compare:
- Transportation and warehousing: 3.5
- Trade, transportation, and utilities: 2.2
- State and local government: 2.1
- Retail trade: 1.8
- Manufacturing: 1.7
- Construction: 1.3
- Leisure and hospitality: 1.4
- Professional and business services: 0.5
- Information: 0.4
- Finance and insurance: 0.1
Compare your LTIR against the benchmark for your specific industry, not the overall average. A 1.5 LTIR in transportation and warehousing is well below the industry norm. That same 1.5 in professional services would be three times the average and a serious concern.
Why LTIR Matters for Your Business
A high LTIR does more than flag a safety problem. It directly increases costs. Lost time injuries generate workers’ compensation claims that include both medical bills and wage replacement for missed work, making them the most expensive type of claim. A pattern of these claims raises your Experience Modification Rate (EMR), which is the multiplier insurers use to set your premiums. Higher EMR means higher insurance costs, sometimes dramatically so.
Many general contractors and project owners also require subcontractors to report their LTIR before awarding work. In construction, oil and gas, and manufacturing, a high LTIR can disqualify you from bidding on projects entirely. Clients view it as a proxy for how well you manage risk on-site.
Recording and Reporting Requirements
The data feeding your LTIR comes from your OSHA 300 Log, which tracks all recordable workplace injuries and illnesses throughout the year. Each lost time case gets a check mark in the “days away from work” column, along with the number of calendar days missed.
Covered employers must electronically submit their OSHA Form 300A summary data through OSHA’s Injury Tracking Application (ITA) by March 2 each year. Starting in 2024, establishments with 100 or more employees in certain industries must also submit detailed information from their OSHA 300 and 301 forms. If you miss the March deadline, you’re still required to submit and can do so through December 31.
Keeping your 300 Log accurate and up to date isn’t just a compliance task. It’s the foundation for calculating a reliable LTIR and identifying patterns before they become expensive problems.