Lost Time Injury Severity Rate (LTISR) Calculator

What is Lost Time Injury Severity Rate (LTISR)?

Lost Time Injury Severity Rate (LTISR) is a key workplace safety KPI that measures the severity of lost time injuries by calculating the total lost workdays due to LTIs relative to manhours worked. It helps organizations understand how serious injuries are, not just how often they occur.

LTISR is often reviewed together with LTIFR:

The formula to calculate LTISR is:

LTISR = (Mandays Lost × Multiplier) ÷ Manhours Worked

A higher LTISR indicates more severe injuries (longer recovery/absence), which affects employee well-being, productivity, and operational continuity. Maintaining a low LTISR supports a strong safety culture, effective risk controls, and credible external reporting.

Important note: LTISR should be calculated using lost time injury cases only (i.e., injuries that resulted in absence from work). Medical treatment or first aid cases should not be included unless your internal standard classifies them as lost time.

Why Do Organizations Measure LTISR?

  • Severity tracking: Identifies whether injuries are leading to long absences and serious outcomes.
  • Management review: Helps leadership focus on high-consequence risks (e.g., falls, machinery, electrical, traffic).
  • Benchmarking: Enables comparison between sites or projects when the same multiplier and definitions are applied.
  • Audit & reporting readiness: Often used in HSE dashboards and management reports aligned to ISO 45001 performance evaluation practices.

Why 1,000,000 / 200,000 / 100,000 Multipliers?

  • 1,000,000 hours is commonly used globally for corporate reporting and benchmarking.
  • 200,000 hours is widely used in OSHA-style reporting (roughly 100 workers working full-time for one year).
  • 100,000 hours is sometimes used for smaller sites/projects to avoid very small decimals.

Rule: Do not compare LTISR results calculated using different multipliers. Standardize the multiplier first.

How to Calculate Lost Time Injury Severity Rate?

To accurately calculate LTISR, you need:

  • Mandays Lost: Total workdays lost due to lost time injuries during the reporting period.
  • Manhours Worked: Total hours worked by the reporting population (employees + contractors as per scope).
  • Multiplier: 1,000,000 / 200,000 / 100,000 (as per your reporting standard).

Worked Example:
If your site had 300 mandays lost over 500,000 manhours worked, using 1,000,000 multiplier:

LTISR = (300 × 1,000,000) ÷ 500,000
LTISR = 300,000,000 ÷ 500,000
LTISR = 600.00

This means 600 mandays were lost per 1,000,000 man-hours, indicating high injury severity and a need to strengthen critical risk controls.

LTISR Calculator – Quick & Easy

Use the free LTISR Calculator below to quickly find your organization's Lost Time Injury Severity Rate. Select the multiplier used in your company reporting.

Result:

Your result will appear here

Tip: Review LTISR with LTIFR and leading indicators (near misses, unsafe conditions, CAPA closure) to avoid under-reporting bias.

How to Interpret LTISR

  • High LTISR: Injuries are leading to long absences (focus on critical risk controls, supervision, and high-risk tasks).
  • Low LTISR with high LTIFR: Many injuries but short absences (focus on prevention and early intervention).
  • Low LTISR and low LTIFR: Typically good performance (verify reporting maturity and leading indicators).
  • Sudden drop to zero: Can be improvement or under-reporting—check near misses and first aid usage.

Why Tracking LTISR is Important?

  • Regulatory & audit visibility: Commonly presented in management reviews and HSE dashboards aligned with ISO 45001 performance evaluation.
  • Cost & productivity impact: Lost days directly affect productivity, overtime costs, morale, and workforce planning.
  • Better risk prioritization: Highlights high-consequence hazards that need stronger controls and verification.
  • Benchmarking: Enables comparisons across sites when definitions and multipliers are consistent.

How to Reduce Lost Time Injury Severity Rate?

  • Strengthen critical controls for high-risk activities (working at height, vehicle movement, lifting, machinery, electrical).
  • Improve supervision and permit-to-work compliance for non-routine work.
  • Conduct effective incident investigations and implement sustainable CAPA (not temporary fixes).
  • Implement competency-based training for operators, supervisors, and contractors.
  • Use safety observations and near-miss reporting to prevent serious injuries before they occur.

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Common Reference Practices (Standards & Guidance)

  • ISO 45001 emphasizes monitoring and evaluation of OH&S performance using suitable indicators.
  • OSHA-style reporting commonly uses a 200,000-hour base for rate calculations in some reporting contexts.
  • ILO OSH guidance promotes use of both lagging and leading indicators for meaningful performance monitoring.

Note: Requirements and definitions vary by country and corporate policy. Always follow your organization’s documented HSE KPI definitions.

Conclusion

Monitoring your organization's Lost Time Injury Severity Rate (LTISR) is essential for building a safer workplace. LTISR helps you understand the impact of injuries in terms of lost workdays, strengthening safety programs and management decision-making.

Use our free LTISR calculator to make safety reporting easier, consistent, and more actionable.

If you found this tool helpful, bookmark this page or share it with your EHS team!

Lost Time Injury Severity Rate Calculator


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