Calculations follow commonly used HSE practices. Always confirm with your organizationβs definitions and local regulations. References: OSHA 1904, ISO 45001, ILO OSH.
The Severity Rate Calculator is an essential safety tool that measures the impact of workplace incidents in terms of lost workdays.
Inputs
Enter details, preview, and export to PDF.
Project / Site
Load Example
These fill in realistic values so students can see how each section is completed.
SR Inputs
Severity Rate (SR) = Lost Days Γ Rate Base Γ· Total Man-Hours
Note for students: What data you need & how to calculate SR
Data needed
- Lost days in the period (define your scope: only days away, or days away + restricted + transferred as per your policy).
- Total man-hours for the same period (employees + contractors; include overtime hours).
- Rate base (1,000,000 or 200,000)βuse consistently month-to-month.
- Scope & period must match across all inputs (same site(s), same dates).
Ways to get Lost days
- Sum the days away recorded per case.
- If your standard includes restricted/transfer days, add those too.
- Use the helper table below to total per-case days.
Ways to get Total man-hours
- Sum of timesheets/payroll (preferred).
- Access/turnstile logs Γ average productive hours per entry.
- Quick estimate via helper: Workers Γ Hours/Day Γ Days Γ Shifts.
Steps
- Define what counts as a lost day in your course/company.
- Calculate Total lost days and Total man-hours for the period.
- Select your rate base.
- Compute: SR = (Lost Days Γ Base) Γ· Man-Hours. Round to 2 decimals.
Common pitfalls
- Mismatched periods/sites between lost days and man-hours.
- Switching bases across monthsβhurts comparability.
- Missing contractor hours or restricted/transfer days (if your definition includes them).
| Case / Description | Days Lost | Remove |
|---|---|---|
| Helper Sum | 0 |
Severity Rate (SR) Report
Generated preview β review and export to PDF
Generated On
Project / Site: β
Client: β
Location: β
Period: β
Rate Base: Per 1,000,000 hrs
SR = (Lost Days Γ Base) Γ· Man-Hours
Lost Days
0
Base
1,000,000
Man-Hours
0
SR
0.00
= (Lost Days Γ Base) Γ· Man-Hours
π Severity Rate Calculator β Complete Guide
In occupational health and safety (HSE), the Severity Rate (SR) is a key performance indicator that measures how severe accidents are in terms of lost workdays.
Where the Frequency Rate (FR) measures how often incidents happen, the SR focuses on their impact. It shows the average number of days lost per 1,000,000 (International) or per 200,000 (OSHA) man-hours worked.
This guide explains the formula, importance, practical examples, and how to use our free Severity Rate Calculator.
β What Is Severity Rate (SR)?
Severity Rate (SR) represents the average severity of injuries in terms of lost workdays relative to exposure hours.
- A low SR β minor injuries, fewer lost days.
- A high SR β severe accidents, long absences.
π Example:
If a site records 50 lost days over 1,000,000 man-hours, the SR = 50 (International Method).
π Formula for Severity Rate (SR)
International Method (ILO / ISO):
SR = (Total Lost Workdays Γ 1,000,000) Γ· Total Man-Hours Worked
OSHA Method (USA):
SR = (Total Lost Workdays Γ 200,000) Γ· Total Man-Hours Worked
π How to Use the Severity Rate Calculator
- Enter Total Man-Hours Worked β Include both employees and contractors.
- Enter Total Lost Workdays β Count all days lost due to LTIs.
- Select Method β OSHA (200,000) or International (1,000,000).
- Click Calculate β Get the Severity Rate instantly.
π Example Calculations for Severity Rate Calculator
Example 1 β Construction Project
- Man-Hours: 2,000,000
- Lost Workdays: 60
International Method (1M):
SR = (60 Γ 1,000,000) Γ· 2,000,000 = 30
OSHA Method (200k):
SR = (60 Γ 200,000) Γ· 2,000,000 = 6
Example 2 β Manufacturing Plant
- Man-Hours: 1,500,000
- Lost Workdays: 25
International Method (1M):
SR = (25 Γ 1,000,000) Γ· 1,500,000 = 16.7
OSHA Method (200k):
SR = (25 Γ 200,000) Γ· 1,500,000 = 3.3
Example 3 β Oil & Gas Operation
- Man-Hours: 10,000,000
- Lost Workdays: 200
International Method (1M):
SR = (200 Γ 1,000,000) Γ· 10,000,000 = 20
OSHA Method (200k):
SR = (200 Γ 200,000) Γ· 10,000,000 = 4
π Why Is Severity Rate Important?
- Measures impact β Not just frequency, but seriousness of accidents.
- Mandatory in reports β Clients and tenders often request both FR & SR.
- Helps performance tracking β Reveals trends over time.
- Ensures compliance β Required by OSHA, ILO, and ISO standards.
ποΈ Real-World Examples
- Metro Rail Project β 20 lost days, 5,000,000 hours β SR = 4.0 (Intl) / 0.8 (OSHA).
- Oil Refinery β 150 lost days, 20,000,000 hours β SR = 7.5 (Intl) / 1.5 (OSHA).
- Power Plant Shutdown β 40 lost days, 500,000 hours β SR = 80 (Intl) / 16 (OSHA).
π Common Mistakes in Calculating Severity Rate
β Not counting contractor hours.
β Counting partial days instead of full days.
β Using wrong multiplier (200k vs 1M).
β Rounding off too early.
π Best Practices to Reduce Severity Rate
β Improve accident investigation & root cause analysis.
β Offer light or modified duties to reduce lost days.
β Strengthen medical care and early rehabilitation.
β Provide better training for high-risk tasks.
β Enforce permit-to-work and audits.
β Frequently Asked Questions (FAQ) on Severity Rate Calculator
Q1: Which method should I use β 200k or 1M?
- OSHA (200k) β USA
- International (1M) β Common worldwide
Q2: Do near-misses affect SR?
No β β Only incidents with lost workdays count.
Q3: Can SR be zero?
Yes β
β if no workdays were lost in the reporting period.
π― Final Thoughts on Severity Rate Calculator
The Severity Rate (SR) shows how much impact incidents have in terms of lost days.
By using our free calculator, you can:
β Calculate SR (OSHA & Intl).
β Benchmark safety performance.
β Present reliable reports to clients and auditors.
π‘ Pro Tip: Always combine Severity Rate (SR) with Frequency Rate (FR), TRIR, and Safe Man Hours for a complete HSE performance picture.
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