Total Lost Time Injury (LTI) Calculation – Complete Guide for Safety Professionals
Workplace injuries can disrupt productivity, increase costs, and harm employee morale. Among different safety indicators, the Lost Time Injury (LTI) is one of the most important because it reflects the number of incidents where workers were unable to return to work for at least one full shift after an accident.
Total Lost Time Injuries (LTI) are used globally as a key measure of safety performance. They form the basis for calculating KPIs such as Safe Manhours, Frequency Rate (FR), Severity Rate (SR), and TRIR.
This guide explains what LTI means, how to calculate it, why it’s important, examples, and reporting practices.
🔹 What is a Lost Time Injury (LTI)?
A Lost Time Injury (LTI) is any work-related incident that results in an employee being unable to return to work for at least one scheduled workday or shift after the accident.
👉 Examples of LTIs include:
- A fractured bone requiring recovery time.
- Severe cuts requiring rest before resuming duties.
- Electrical shocks leading to hospital admission.
- Major sprains or back injuries preventing immediate return to work.
❌ Not counted as LTI:
- First aid cases.
- Medical treatment where the worker can still work the same or next day.
- Restricted work cases (counted separately under OSHA recordables).
🔹 Formula for Total Lost Time Injuries
Unlike FR, SR, or IR, the Total LTI itself is simply a count of cases.
Total LTI = Count of all incidents that caused employees to miss at least one full work shift/day
However, LTIs are often used in formulas such as:
- Safe Manhours = Hours worked without LTI
- FR (Frequency Rate) = (LTIs × 1,000,000) ÷ Total Manhours
- AFR (Accident Frequency Rate, ILO) = (LTIs × 1,000,000) ÷ Total Manhours
🔹 Example of LTI Calculation
Example 1:
- A project had 5 accidents in one year.
- Out of these, 2 required only first aid, 1 was a restricted work case, and 2 resulted in workers missing shifts.
✅ Total LTI = 2
Example 2 (Including in KPI):
- Total LTI = 3
- Total manhours = 2,000,000
AFR = (3 × 1,000,000) ÷ 2,000,000
AFR = 1.5
✅ The Accident Frequency Rate (based on LTIs) = 1.5.
🔹 Why is LTI Important?
- Measures Serious Incidents – LTIs highlight the more significant accidents, not minor ones.
- Key KPI Component – Used in FR, SR, and AFR calculations.
- Client & Regulator Reporting – Many clients demand monthly LTI statistics.
- Benchmarking – Industry standards often compare LTIs per year.
- Motivational Milestones – Sites celebrate “X days without LTI” to encourage safe behavior.
🔹 Lost Days vs Lost Time Injuries
- Lost Time Injuries (LTI): Count of cases where workers missed at least one shift.
- Lost Days: Total days lost due to LTIs.
👉 Example:
- 2 LTIs occurred.
- One worker lost 5 days, another lost 10 days.
✅ Total LTI = 2
✅ Total Lost Days = 15
🔹 Limitations of LTI as a KPI
- Does Not Include Minor Injuries: Focuses only on severe enough cases.
- Lagging Indicator: Shows what already happened, not future risks.
- Different Reporting Standards: Some countries/companies count calendar days, others only workdays.
- Can Be Misleading: A site with few LTIs but many restricted cases may still look “good.”
🔹 How to Reduce LTIs
- Strengthen risk assessment and preventive measures.
- Provide PPE and ensure compliance.
- Conduct toolbox talks and regular safety training.
- Implement Permit-to-Work systems for high-risk activities.
- Encourage near-miss reporting to prevent serious accidents.
- Improve emergency response to minimize injury severity.
🔹 Case Study Example
A refinery project recorded the following in one year:
- Total manhours = 10,000,000
- Accidents = 12
- 5 First Aid cases
- 4 Medical Treatment cases
- 2 Lost Time Injuries
- 1 Fatality (counted as an LTI, often assigned 6,000 lost days)
✅ Total LTI = 3 (2 + 1 fatality)
🔹 LTI in Safety Reports
- Monthly Reports: “Project has achieved 2 million safe manhours without LTI.”
- Annual Reports: Companies summarize total LTIs for the year.
- Client Audits: LTIs are reviewed during contractor evaluations.
- On-Site Boards: “X Days Without LTI” displayed prominently.
🔹 FAQs on LTI
Q1. What qualifies as an LTI?
👉 Any case where a worker misses at least one full shift due to a work-related injury.
Q2. Do fatalities count as LTIs?
👉 Yes. Most organizations count them as LTIs (with 6,000 lost days assigned for severity calculations).
Q3. Is LTI used worldwide?
👉 Yes, but reporting definitions may differ slightly by country/company.
Q4. Can LTI be zero?
👉 Yes. Many projects aim for “Zero LTI” culture.
Q5. How is LTI different from TRIR?
👉 LTI counts only serious injuries leading to absence. TRIR includes all OSHA recordables (LTI + RWC + MTC + fatalities).
🔹 LTI Calculator – Free Tool
To simplify calculations, we’ve provided a Lost Time Injury Calculator on 👉 The HSE Tools.
✅ Features:
- Enter total LTIs and manhours.
- Get automatic AFR, FR, and Safe Manhours impact.
- Download your results as a PDF report.
- 100% free for safety officers, auditors, and students.
👉 Try it here: Lost Time Injury (LTI) Calculator – The HSE Tools
🔹 Conclusion
Lost Time Injuries (LTI) are one of the most widely reported safety statistics. By tracking LTIs, organizations can identify serious incidents, celebrate safe manhours, and improve their safety performance.
👉 Key Takeaway:
- LTI = Cases where workers missed at least one full shift/day due to workplace injury.
- LTIs are used in formulas like Safe Manhours, FR, SR, and TRIR.
- Reducing LTIs requires strong safety culture, training, and leadership commitment.
🔗 External References
- International Labour Organization (ILO) – Safety and Health Statistics
- OSHA Recordkeeping Guidelines
Total Recordable Incident Rate (TRIR) – Complete Guide for Safety Professionals
Incident Rate (IR) – Complete Guide for Safety Professionals
Severity Rate (SR) – Complete Guide for Safety Professionals
Frequency Rate (FR) – Complete Guide for Safety Professionals
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