How to Calculate Lost Time Incident Rate (LTIR)

Lost Time Incident Rate (LTIR) is one of the most important safety metrics organizations track. It measures how often workers are injured seriously enough to miss work. A high LTIR indicates that your organization is experiencing serious injuries that disrupt operations and signal safety program failures. A low LTIR demonstrates that your safety program is effectively preventing serious incidents.

Yet many organizations struggle with calculating LTIR correctly. Is it the same as LWCR? How do you account for employees who work part-time? What counts as "lost time"? Should you include contractors? When regulations require OSHA reporting and audits verify LTIR accuracy, getting the calculation right matters.

This guide provides a complete roadmap for understanding, calculating, benchmarking, and reducing Lost Time Incident Rate.

What Is Lost Time Incident Rate (LTIR)?

Lost Time Incident Rate is a metric measuring how frequently workers are injured seriously enough to miss work. It provides a standardized way to compare safety performance across organizations of different sizes, industries, and geographic locations.

The Core Concept

LTIR counts incidents where a worker cannot return to work on the day following injury or cannot work their next scheduled shift. These are among the most serious workplace incidents—they represent injuries significant enough to prevent the worker from performing their job duties.

Unlike TRIR (Total Recordable Incident Rate), which includes all recordable injuries and illnesses, LTIR focuses specifically on the most serious incidents. This focus makes LTIR valuable for:

• Identifying whether safety programs prevent serious injuries
• Understanding true injury severity
• Directing resources to the highest-impact prevention efforts
• Demonstrating genuine safety program effectiveness to regulators

What Counts as Lost Time

Lost time incidents include injuries or illnesses where:

• The worker cannot work their next scheduled shift
• Medical treatment beyond first aid is required
• The injury prevents normal job duty performance
• The incident is work-related

Examples that count:

• A worker with a broken leg who cannot work for 3 weeks
• A worker with a severe burn requiring hospitalization
• A worker with a back injury preventing lifting for several weeks
• A worker with a serious chemical exposure requiring treatment

Examples that don't count:

• A minor cut treated with first aid, worker returns next day
• A worker who takes a sick day unrelated to work
• A worker who requests time off for personal reasons
• Incidents treated at the scene with no lost time

The distinction is critical: LTIR measures only incidents where lost time actually occurred, not incidents that could have caused lost time or where the worker voluntarily took time off.

How to Calculate Lost Time Incident Rate (LTIR)

LTIR calculation follows a standardized formula that allows comparison across organizations.

The LTIR Formula

LTIR = (Number of Lost Time Incidents × 200,000) ÷ Total Hours Worked

The 200,000 figure is a standardization factor representing hours worked by 100 full-time employees over one year (100 employees × 40 hours/week × 50 weeks/year = 200,000 hours). This allows organizations of any size to be compared on an equal basis.

Step-by-Step Calculation

Step 1: Identify and Count Lost Time Incidents

Review all incidents during your calculation period (typically one calendar year). For each incident, determine whether it qualifies as a lost time incident:

• Did the worker miss their next scheduled shift?
• Was the absence work-related?
• Did the incident require medical treatment beyond first aid?

Document each lost time incident separately with:

• Date of incident
• Worker identification
• Description of incident
• Date lost time began
• Date worker returned to full duty
• Classification (type of injury/illness)

Example: If you had 15 recordable incidents during the year but only 5 resulted in lost time, your count is 5 lost time incidents.

Step 2: Calculate Total Hours Worked

Determine total hours worked by all employees during the calculation period. This includes:

• Hours worked by full-time employees
• Hours worked by part-time employees
• Hours worked by temporary workers
• Hours worked by contractors (if included in your safety program)

Do NOT include:

• Vacation time
• Sick time
• Unpaid leave
• Time employees were off work for any reason

Total hours should align with your payroll records. For example, if you have:

• 50 full-time employees working 40 hours/week, 50 weeks/year = 100,000 hours
• 20 part-time employees working 20 hours/week, 50 weeks/year = 20,000 hours
• Total = 120,000 hours worked

Step 3: Apply the Formula

LTIR = (Number of Lost Time Incidents × 200,000) ÷ Total Hours Worked

Calculation Example:

• Lost time incidents: 3
• Total hours worked: 120,000
• LTIR = (3 × 200,000) ÷ 120,000
• LTIR = 600,000 ÷ 120,000
• LTIR = 5.0

This organization's LTIR is 5.0, meaning 5 lost time incidents per 100 workers annually.

Step 4: Verify and Document

• Double-check your incident count and hours worked
• Ensure classifications are consistent
• Document methodology so calculations are repeatable
• Maintain records for regulatory compliance

Using an LTIR Calculator

Many organizations use spreadsheet-based LTIR calculators to streamline the process. A basic calculator should:

• Allow entry of lost time incident count
• Allow entry of total hours worked
• Automatically apply the formula
• Show results clearly
• Allow comparison to previous periods

When using a calculator, ensure it matches your organization's specific requirements—whether you include contractors, how you count part-time hours, and whether you use different calculation periods.

LTIR vs. Other Safety Metrics: Understanding the Differences

Organizations typically track multiple safety metrics. Understanding how LTIR relates to others provides complete safety picture.

LTIR vs. TRIR (Total Recordable Incident Rate)

TRIR includes all OSHA-recordable injuries and illnesses: those requiring medical treatment beyond first aid, days away from work, restricted work, job transfers, or medical treatment.

LTIR includes only incidents resulting in lost time.

Comparison example:

• TRIR = 5.0 (5 recordable incidents per 100 workers annually)
• LTIR = 1.5 (1.5 lost time incidents per 100 workers annually)

This means most incidents are minor or involve restricted duty, not lost time. A facility might have frequent minor incidents but good control of serious incidents.

LTIR vs. DART (Days Away, Restricted, or Transferred)

DART includes:

• Days away from work
• Restricted work cases
• Job transfer cases

LTIR includes only days away from work.

A worker with restricted duty (works in reduced capacity) counts toward DART but not LTIR. This makes DART broader and often higher than LTIR.

LTIR vs. LWCR (Lost Workday Case Rate)

LTIR and LWCR are very similar concepts measuring essentially the same thing—incidents resulting in lost time. Definitions differ slightly:

LTIR can sometimes include incidents where a worker is sent home even though modified duty might have been available.

LWCR specifically measures next scheduled shift lost.

For most organizations, LTIR and LWCR produce nearly identical results.

What Is a Good LTIR? Industry Benchmarks and Standards

"Good" LTIR depends on your industry, organizational risk, and improvement trajectory.

Industry Benchmarks

OSHA publishes industry-average injury rates. While specific LTIR benchmarks are less standardized than TRIR, approximate ranges include:

• Construction: 1.5-2.5 LTIR
• Manufacturing: 0.8-1.5 LTIR
• Healthcare: 1.0-2.0 LTIR
• Retail/Services: 0.5-1.0 LTIR
• Office/Administrative: 0.2-0.5 LTIR

These are general ranges; actual benchmarks vary by specific industry classification.

Evaluating Your LTIR

Rather than focusing solely on absolute numbers, evaluate LTIR from multiple angles:

Comparison to industry: Is your LTIR better or worse than similar organizations? If worse, you have opportunity for improvement.

Trend analysis: Is your LTIR improving, stable, or worsening? Organizations with declining LTIR demonstrate effective safety program efforts. Increasing LTIR suggests problems.

Improvement trajectory: Even if your LTIR is above industry average, consistent year-over-year improvement (10-15% annually) demonstrates effective safety management.

Incident severity: Beyond LTIR, examine average days of lost time. Some organizations have fewer but more severe incidents. Others have more incidents but less severe.

Incident clustering: Is LTIR concentrated in certain departments or processes? This reveals where risk is highest.

Setting LTIR Goals

Set realistic LTIR reduction goals based on:

• Your current baseline
• Industry benchmarks
• Historical performance trends
• Organizational risk profile

A typical goal: 10-15% annual LTIR reduction. Organizations with strong safety programs achieve this consistently. Organizations making dramatic changes (new equipment, process redesign, significant safety investment) might achieve 25-30% reduction.

OSHA Lost Time Incident Rate Requirements

Organizations must understand OSHA's requirements for tracking and reporting LTIR.

OSHA Recording Requirements

OSHA requires employers with 11 or more employees to:

• Record all work-related injuries and illnesses
• Maintain records on OSHA Form 300 (Log of Work-Related Injuries and Illnesses)
• Report Form 300-A (Summary) to OSHA annually
• Preserve records for 5 years

Lost time incidents must be recorded on Form 300 with classification indicating that lost time occurred.

OSHA Reporting and Form 301

When a lost time incident occurs:

• Record on OSHA Form 300 (the log)
• Complete OSHA Form 301 (Injury and Illness Incident Report) with incident details
• Within 24 hours, notify the worker or their representative
• Report serious incidents (hospitalization, amputation, loss of eye) to OSHA

OSHA Recordkeeping Standards

Employers must:

• Accurately classify incidents (lost time vs. restricted duty vs. medical treatment only)
• Record incident dates accurately
• Document that lost time actually occurred
• Maintain records accessible for OSHA inspection

Misclassification of incidents is a common OSHA violation. Incidents classified as lost time must have clear documentation that the worker actually missed work.

Strategies for Reducing LTIR

High LTIR indicates that serious injuries are occurring. Reducing LTIR requires systematic prevention efforts.

Analyze Serious Incident Patterns

Review lost time incidents to identify trends:

• Which departments have most incidents?
• What types of incidents cause lost time?
• Are certain locations higher-risk?
• Do particular jobs or tasks have higher incident rates?
• Are recurring patterns visible?

Pattern analysis reveals where prevention efforts should focus.

Strengthen Hazard Identification

Serious injuries result from uncontrolled hazards. Implement systematic hazard identification:

• Conduct job safety analyses on high-risk work
• Involve workers in identifying hazards
• Review near-misses and minor incidents for warning signs
• Use incident investigation to reveal overlooked hazards

Implement Engineering Controls

Engineering controls—eliminating or reducing hazards through design—are most effective:

• Replace manual tasks with automated equipment
• Redesign workstations to reduce strain
• Install fall protection systems
• Improve lighting to prevent struck-by incidents
• Eliminate chemical hazards through substitution

Enhance Training and Procedure Compliance

Workers must understand hazards and follow safe procedures:

• Provide job-specific safety training
• Ensure procedures document safe work methods
• Verify that workers actually follow procedures
• Provide refresher training when procedures change

Improve Near-Miss Reporting

Near-misses are warnings of serious incidents. Organizations with strong near-miss programs prevent serious injuries:

• Encourage near-miss reporting without fear
• Investigate all near-misses
• Implement corrective actions
• Track near-miss trends

Track Leading Indicators

Leading indicators predict future incidents:

• Near-miss reports
• Hazard observations
• Training completion
• Inspection findings
• Procedure compliance rates

Organizations improving leading indicators see subsequent LTIR improvements.

Frequently Asked Questions About Lost Time Incident Rate (LTIR)

How Do You Calculate Lost Time Incident Rate (LTIR) for a Small Organization?

The LTIR calculation formula is the same regardless of organization size: LTIR = (Number of Lost Time Incidents × 200,000) ÷ Total Hours Worked. However, calculating accurately for small organizations requires careful attention to detail because a single incident has larger proportional impact.

For example, a 10-person organization with 1 lost time incident might have LTIR = 10.0 (one incident per 100 workers annually). This is significantly higher than a 1,000-person organization with 10 lost time incidents (LTIR = 2.0). However, both situations warrant serious investigation.

For small organizations, calculating LTIR is simpler in some ways:

• Tracking total hours worked is easier with fewer employees
• Identifying lost time incidents is more straightforward
• You likely have direct knowledge of incidents

However, it's more critical to calculate accurately because small organization's LTIR will fluctuate with each incident. A single serious incident dramatically changes LTIR. This makes trend analysis important—looking at 2-3 year trends rather than single-year snapshots.

When calculating for small organizations, ensure you count hours worked accurately. Some small organizations undercount hours by not including vacation backfills, temporary workers, or seasonal employees. Total hours must include all hours worked by anyone in your safety program.

What Counts as "Lost Time" for LTIR Calculation, and How Do You Handle Partial Days?

Lost time is when a worker cannot work their next scheduled shift due to work-related injury or illness. The key criterion is "next scheduled shift"—not whether they can work the same day or take partial duty.

Clear scenarios:

• Injured Tuesday afternoon, cannot work Wednesday's shift = lost time
• Injured Tuesday, works Wednesday in restricted duty = not lost time (for LTIR; would count for DART)
• Injured Tuesday morning, treated, returns to work Tuesday afternoon = not lost time

Partial day scenarios are trickier:

• Worker injured, sent home at noon. Next scheduled shift is 4 PM that afternoon. Did they miss "next scheduled shift"? Technically yes, even though only 4 hours. This counts as lost time.
• Worker injured Tuesday, misses half of Wednesday's shift, works afternoon = Generally counts as lost time because next scheduled shift was missed, even partially.

How to handle partial days: Organizations can interpret this differently. Some count any part of next scheduled shift as lost time. Others require full shift loss. The critical thing is consistency—use the same standard year-to-year.

Days of lost time tracking:Some organizations track not just number of incidents but total days lost. This provides additional perspective:

• 2 incidents with 2 days lost each = 4 total days
• 2 incidents with 20 days lost each = 40 total days

Both have same LTIR but dramatically different impact. Many organizations track both incident count and total days lost.

Documentation is essential: Record for each lost time incident:

• Date of incident
• Incident description
• Date lost time began
• Date worker returned to full duty
• Total days/shifts missed

This documentation enables accurate LTIR calculation and provides evidence if OSHA questions classifications.

What's the Difference Between LTIR and OSHA Recordable Rate, and Which Should Organizations Prioritize?

OSHA Recordable Rate (also called TRIR or Total Recordable Incident Rate) is the official OSHA metric and is what organizations report to regulators. LTIR is an internal metric organizations calculate to understand serious injury frequency.

OSHA Recordable Rate includes:

• All medical treatment beyond first aid
• All days away from work
• All restricted work cases
• All job transfer cases
• Certain diagnosed conditions

LTIR includes only:

• Cases with lost time (worker missed next scheduled shift)

Because LTIR is narrower, LTIR is always equal to or lower than OSHA Recordable Rate.

Which should you prioritize?

Organizations must track OSHA Recordable Rate because it's required for regulatory compliance. OSHA recordable rate is what you report to OSHA and what regulators inspect.

However, LTIR is often more meaningful internally because it focuses specifically on serious incidents. A high OSHA Recordable Rate with low LTIR means most incidents are minor or involve restricted duty—better than the alternative, but still indicating safety concerns.

The best practice: Track both metrics. Report OSHA Recordable Rate to regulators. Use LTIR internally to focus prevention efforts on serious incidents. This combination provides complete safety picture.

How Do You Account for Contractors and Temporary Employees in LTIR Calculations?

Whether to include contractors and temporary employees in LTIR calculations is an important decision that affects both incident count and total hours worked.

OSHA requirements: OSHA regulations require that employers include contractor and temporary worker incidents in their OSHA recordable rate. If a contractor working at your site is injured, you must record it.

LTIR calculation: Organizations have more flexibility with LTIR. Some include contractors; some don't. The critical thing is consistency—use the same methodology year-to-year.

Recommended approach:

• If contractors work regularly under your supervision and safety program, include them in LTIR
• If contractors work independently with their own safety programs, exclude them
• If mixed (some contractors under your program, some independent), count only those under your program

Hours accounting: This is critical. If you include contractor lost time incidents, you must also include their hours worked in total hours calculation. Excluding hours while including incidents would artificially inflate LTIR.

Example:

• Your employees: 500,000 hours, 3 lost time incidents
• Contractor employees: 50,000 hours, 1 lost time incident

If including contractors:

• Total hours: 550,000
• Total incidents: 4
• LTIR = (4 × 200,000) ÷ 550,000 = 1.45

If excluding contractors:

• Total hours: 500,000
• Total incidents: 3
• LTIR = (3 × 200,000) ÷ 500,000 = 1.20

Consistency matters more than which approach you choose. Document your methodology and apply it consistently.

How Do You Reduce LTIR When You Have Multiple Locations or Departments with Different Risk Levels?

When LTIR varies significantly across locations or departments, targeted improvement requires analyzing and addressing location or department-specific issues.

Step 1: Calculate location/department-specific LTIR. Rather than single organization LTIR, calculate for each location or department. This reveals which areas drive overall LTIR and where to focus efforts.

Step 2: Identify patterns. For high-LTIR locations or departments, analyze what's different:

• What types of work create highest risk?
• What hazards are present?
• Are procedures or training different?
• Are certain supervisors associated with more incidents?
• Are certain worker populations at higher risk?

Step 3: Investigate root causes. Conduct deeper investigation of high-LTIR areas. Incident investigations should reveal systematic issues, not just individual failures.

Step 4: Implement location-specific interventions. Based on patterns, implement targeted controls:

• Enhanced training specific to high-risk work
• Engineering controls addressing location-specific hazards
• Procedure modifications
• Supervision enhancements
• Equipment or facility improvements

Step 5: Share best practices. When low-LTIR locations are doing something that high-LTIR locations aren't, analyze what's working and transfer those practices.

Step 6: Benchmark between locations. When multiple locations operate similar processes, benchmark performance. Why does Location A have 1.5 LTIR while Location B has 3.2? Understanding differences enables improvement.

Step 7: Set location-specific goals. Rather than single organization goal, set realistic goals for each location based on current performance and risk. High-risk locations might target 15-20% annual improvement; low-risk locations might maintain current performance.

This location-specific approach focuses resources where risk is highest and enables meaningful improvement rather than averaging high and low performers.