Lost Time Injury Severity Rate Calculation

Safely calculate and understand your organization's Lost Time Injury Severity Rate.

Calculation Results

Formula Explanation:
The Lost Time Injury Severity Rate (LTISR) is calculated to measure the impact of lost-time injuries on productivity and safety performance.

LTISR (Per 100,000 Hours) = (Total Lost Time Days * 200,000) / Total Hours Worked

The 200,000 factor represents the number of hours 100 employees would work in a 40-hour week, 50-week year (100 employees * 40 hours/week * 50 weeks/year = 200,000 hours).

The LTISR Per Year is a simple annualization: LTISR (Per Year) = LTISR (Per 100,000 Hours) / Reporting Period (Years). This helps normalize rates over different reporting durations.

LTISR Trend Visualization

LTISR Comparison: Calculated vs. Target

Key Performance Indicators

Summary of Input and Calculated Values

Metric	Value	Unit
Total Lost Time Days	—	Days
Total Hours Worked	—	Hours
LTISR (Per 100,000 Hours)	—	Rate
LTISR (Per Year)	—	Rate/Year

What is the Lost Time Injury Severity Rate (LTISR)?

The Lost Time Injury Severity Rate (LTISR) is a critical workplace safety metric that measures the frequency and impact of injuries resulting in an employee being unable to perform their regular job duties for at least one full day or shift. Unlike incidence rates (which focus on the number of injuries), the severity rate specifically quantifies the duration of lost work time, providing deeper insight into the actual cost and disruption caused by workplace incidents. This metric is essential for understanding the overall effectiveness of a company's safety programs and identifying areas for improvement.

Who should use it?

• Health and Safety Managers
• Risk Assessors
• Operations Directors
• HR Professionals
• Compliance Officers
• Any organization aiming to reduce workplace accidents and their consequences.

Common Misunderstandings:

• Confusing LTISR with LTIR (Lost Time Injury Frequency Rate): While related, LTIR counts the number of lost-time injuries per million hours worked, whereas LTISR focuses on the total days lost relative to hours worked. A low LTIR doesn't always guarantee a low LTISR if the few injuries that do occur are severe.
• Ignoring the "Severity" Aspect: Some may look at only the number of incidents, failing to understand the significant productivity and financial impact of prolonged absences.
• Inconsistent Reporting Periods: Calculating LTISR over different durations without proper annualization can make comparisons difficult. Our calculator helps by providing an annual rate.

LTISR Formula and Explanation

The most common formula for calculating the Lost Time Injury Severity Rate (LTISR) is based on the total number of days lost due to injuries, normalized against the total hours worked, and often expressed per 100,000 hours for easier interpretation.

The Standard Formula (often used by regulatory bodies):

LTISR = (Total Lost Time Days * 200,000) / Total Hours Worked

Where:

• Total Lost Time Days: The aggregate number of days employees were unable to work due to work-related injuries during the reporting period. This includes days of work missed, not necessarily calendar days.
• Total Hours Worked: The sum of all hours actually worked by all employees during the same reporting period.
• 200,000: This is a standard industry factor representing the equivalent number of hours worked by 100 employees, each working 40 hours per week for 50 weeks per year (100 employees * 40 hours/week * 50 weeks/year = 200,000 hours). This allows for a standardized comparison across different sized workforces and industries.

Annualized LTISR:

To compare rates across different reporting periods or to a specific year, an annualized rate is useful:

LTISR (Per Year) = LTISR (Per 100,000 Hours) / Reporting Period (in Years)

Variables Table

Variable	Meaning	Unit	Typical Range / Notes
Total Lost Time Days	Sum of days employees couldn't work due to injury	Days	Non-negative integer (e.g., 0, 15, 120)
Total Hours Worked	Aggregate hours worked by all employees	Hours	Non-negative number (e.g., 50000, 250000, 1000000)
Reporting Period	Duration of the assessment	Years	Typically 1, but can be fractional (e.g., 0.5 for 6 months)
LTISR (Per 100,000 Hours)	Severity rate normalized	Rate per 100,000 hours	Usually a non-negative decimal (e.g., 0.75, 3.5, 10.2)
LTISR (Per Year)	Severity rate normalized to one year	Rate per year	Non-negative decimal, useful for annual tracking

Practical Examples

Example 1: Small Manufacturing Company

A small factory reports the following for the past year:

• Total Lost Time Days: 30 days (due to two significant injuries).
• Total Hours Worked: 150,000 hours.
• Reporting Period: 1 Year.

Calculation:

• LTISR = (30 * 200,000) / 150,000 = 6,000,000 / 150,000 = 40.0
• LTISR (Per Year) = 40.0 / 1 = 40.0

Result: The LTISR is 40.0 per 100,000 hours worked. This indicates a moderate level of severity in lost-time injuries for this period.

Example 2: Large Construction Project

A large construction project tracked its performance over 6 months (0.5 years):

• Total Lost Time Days: 150 days (due to several serious incidents).
• Total Hours Worked: 400,000 hours.
• Reporting Period: 0.5 Years.

Calculation:

• LTISR = (150 * 200,000) / 400,000 = 30,000,000 / 400,000 = 75.0
• LTISR (Per Year) = 75.0 / 0.5 = 150.0

Result: The LTISR is 75.0 per 100,000 hours worked. The annualized rate of 150.0 per year highlights a high severity of injuries on this project, requiring urgent safety interventions.

How to Use This LTISR Calculator

1. Gather Your Data: Collect the accurate figures for 'Total Lost Time Days' and 'Total Hours Worked' for the specific period you want to analyze. Ensure these are work-related injuries that resulted in at least one day away from work.
2. Determine Reporting Period: Input the duration of your reporting period in years. For a standard annual report, use '1'. For a semi-annual report, use '0.5'.
3. Enter Values: Input the collected numbers into the respective fields: 'Total Lost Time Days', 'Total Hours Worked', and 'Reporting Period (Years)'.
4. Calculate: Click the "Calculate LTISR" button.
5. Interpret Results: The calculator will display the calculated LTISR per 100,000 hours and the annualized LTISR. Review the intermediate values and the formula explanation to understand how the rate was derived.
6. Compare and Analyze: Use the calculated rate to benchmark your safety performance against previous periods, industry averages, or internal targets. The chart provides a visual comparison.
7. Reset: If you need to perform a new calculation, click "Reset" to clear all fields to their default values.
8. Copy: Use the "Copy Results" button to easily transfer the key figures for reporting or analysis.

Selecting Correct Units: The calculator uses standard units (days and hours). Ensure your input data is consistent. The primary result is standardized per 100,000 hours, making it comparable across different organizations.

Interpreting Results: A lower LTISR generally indicates better workplace safety and less disruption from injuries. However, context is crucial. Compare your rate to industry benchmarks and track trends over time rather than focusing on a single number in isolation.

Key Factors That Affect LTISR

1. Nature of Work Hazards: Industries with inherently higher risks (e.g., construction, mining, heavy manufacturing) tend to have higher LTISR due to the potential severity of incidents.
2. Effectiveness of Safety Training: Comprehensive and regular training equips employees with the knowledge to avoid hazards and respond correctly, reducing both the frequency and severity of injuries.
3. Implementation of Safety Procedures: Robust safety protocols, including permits-to-work, lockout/tagout, and emergency response plans, directly mitigate risks that could lead to lost time.
4. Use of Personal Protective Equipment (PPE): Consistent and correct use of appropriate PPE can significantly reduce the severity of injuries when accidents do occur.
5. Workplace Culture: A strong safety culture, where employees feel empowered to report hazards and near misses without fear of reprisal, is crucial for proactive risk management.
6. Equipment Maintenance and Housekeeping: Poorly maintained machinery or cluttered work areas are common sources of accidents. Regular maintenance and good housekeeping practices prevent many incidents.
7. Management Commitment: Visible and active commitment from leadership to prioritize safety sends a powerful message throughout the organization and influences resource allocation for safety initiatives.
8. Employee Engagement: When employees are actively involved in safety committees, risk assessments, and incident investigations, it fosters a shared responsibility for maintaining a safe workplace.

FAQ

Q1: What is the difference between LTISR and TRIR (Total Recordable Incident Rate)?

A1: TRIR measures all work-related injuries and illnesses requiring medical treatment beyond first aid, per million hours worked. LTISR specifically focuses on injuries that cause an employee to miss at least one full day of work, measuring the *severity* of lost time, not just the recording of an incident.

Q2: Does LTISR include fatalities?

A2: Yes, fatalities are typically counted as a specific number of lost workdays depending on the regulatory standard (often 6,000 days per fatality) to reflect their ultimate severity in the calculation.

Q3: What is considered a "lost time day"?

A3: A lost time day is a day on which an employee was unable to perform their regular job duties due to a work-related injury or illness. This typically means they are medically advised not to work or are on paid/unpaid leave because of the injury.

Q4: Can I use calendar days instead of workdays lost?

A4: It's best practice to use actual workdays missed. Some standards may have specific definitions, but generally, it refers to scheduled shifts or workdays the employee could not attend.

Q5: What if my company works 24/7? How do I calculate Total Hours Worked?

A5: Sum the actual hours worked by every employee during the reporting period. For continuous operations, this means accounting for all shifts, including overtime, worked by all personnel.

Q6: How often should I calculate my LTISR?

A6: It's recommended to calculate LTISR at least annually for official reporting. However, monitoring it quarterly or even monthly can help identify emerging trends and allow for more timely interventions.

Q7: What is a "good" LTISR?

A7: A "good" LTISR is typically low, ideally close to zero. However, the definition of good also depends on your industry. Compare your rate to industry averages and focus on reducing your own rate over time.

Q8: Can the calculator handle different reporting periods like 18 months?

A8: Yes, you can input the reporting period in years. For 18 months, you would enter '1.5' into the 'Reporting Period (Years)' field. The calculator will correctly annualize the rate.

Q9: How does changing 'Total Hours Worked' impact the LTISR?

A9: Since 'Total Hours Worked' is in the denominator of the LTISR formula, increasing it (while keeping lost days constant) will decrease the LTISR. This reflects improved efficiency or a larger workforce spreading the impact of lost days over more total work.