HSE Calculators — Free Open-Source Safety Metrics Library

30+ health, safety & environment (HSE) calculators — TRIR, LTIR, LTIFR, DART, EMR, severity rate, heat stress (WBGT), noise exposure, hand-arm vibration, ergonomics (REBA, RULA, NIOSH), fire load, evacuation time, manhours, risk matrix, incident cost, and more. Pure TypeScript, zero runtime dependencies, MIT licensed.

The most comprehensive open-source occupational health and safety (OHS) metrics library available. Every formula references the exact regulation (OSHA 29 CFR, HSE UK, ISO 45001, ILO, NIOSH, ACGIH) it is sourced from. Used by construction, oil & gas, manufacturing, utilities, mining, and industrial teams worldwide.

🌐 Live calculators: tools.smartqhse.com — no signup, no ads, free forever. 🏗️ Full HSE platform: smartqhse.com — AI-powered permits, risk assessments, incidents, audits, ISO 45001 compliance.

Table of contents

• Installation
• Quick start
• Available calculators
• Incident rate formulas
• Occupational exposure
• Ergonomics
• Environmental
• Fire safety
• Workload & productivity
• Risk scoring
• Regulation citations
• Contributing
• License

Installation

npm install @smartqhse/hse-calculators
# or
pnpm add @smartqhse/hse-calculators
# or
yarn add @smartqhse/hse-calculators

Zero runtime dependencies. Tree-shakeable. Node 18+, works in the browser, Deno, Bun, edge runtimes.

Quick start

import { calculateTRIR, calculateLTIFR, calculateWBGT } from "@smartqhse/hse-calculators";

// TRIR — OSHA Total Recordable Incident Rate (29 CFR 1904.7)
const trir = calculateTRIR({ recordableIncidents: 3, hoursWorked: 500_000 });
// → { rate: 1.2, base: 200_000, formula: "(3 × 200,000) ÷ 500,000" }

// LTIFR — ISO/ILO Lost Time Injury Frequency Rate
const ltifr = calculateLTIFR({ lostTimeInjuries: 3, hoursWorked: 500_000 });
// → { rate: 6, base: 1_000_000, formula: "(3 × 1,000,000) ÷ 500,000" }

// WBGT — Heat stress (ACGIH TLV)
const heat = calculateWBGT({ tempC: 38, humidity: 60, globeTempC: 42 });
// → { wbgt: 34.1, riskLevel: "high", acgihWorkRestRatio: "25/75" }

Available calculators

Incident rate formulas

The "four big ratios" every HSE manager tracks. All return rate + base + formula string so you can audit the calculation.

| Function | Measures | Base | Regulation | |---|---|---|---| | calculateTRIR | Total Recordable Incident Rate (OSHA) | 200,000 | 29 CFR 1904.7 | | calculateLTIR | Lost Time Incident Rate (OSHA) | 200,000 | 29 CFR 1904.7(b)(3) | | calculateLTIFR | Lost Time Injury Frequency Rate (ISO/ILO) | 1,000,000 | ILO / ISO 45001:2018 | | calculateDART | Days Away, Restricted, Transferred | 200,000 | 29 CFR 1904.7(a) | | calculateSeverityRate | Days lost per 200k/1M hours | 200,000 or 1,000,000 | OSHA / ILO | | calculateFrequencyRate | Accident frequency (international) | 1,000,000 | HSE UK / IOGP | | calculateEMR | Experience Modification Rate (workers comp) | — | NCCI | | calculateIncidentCost | Direct + indirect cost per incident | — | OSHA $afety Pays | | calculateHeinrichRatio | Near-miss pyramid ratios | — | Heinrich/Bird | | calculateSafeDays | Days since last recordable | — | — | | calculateWorkingDaysLost | Total productive days lost | — | ISO 45001 |

Occupational exposure

| Function | Measures | Units | Regulation | |---|---|---|---| | calculateNoiseDose | Daily noise dose (LEX,8h) | dB(A) | OSHA 29 CFR 1910.95 | | calculateNoiseExposure | Time-weighted noise exposure | dB(A) | ACGIH TLV / EU 2003/10/EC | | calculateHAV | Hand-Arm Vibration dose | A(8) m/s² | HSE UK L140 | | calculateWBV | Whole-Body Vibration dose | A(8) m/s² | ISO 2631-1 | | calculateChemicalExposure | TWA chemical exposure | mg/m³ | OSHA PEL / ACGIH TLV | | calculateCOSHHExposure | COSHH workplace exposure | WEL | HSE UK EH40 | | calculateCOSHHRiskScore | COSHH risk banding | 1–4 | HSE UK COSHH Essentials |

Ergonomics

| Function | Measures | Scale | Source | |---|---|---|---| | calculateREBA | Rapid Entire Body Assessment | 1–15 | Hignett & McAtamney 2000 | | calculateRULA | Rapid Upper Limb Assessment | 1–7 | McAtamney & Corlett 1993 | | calculateNIOSHLift | NIOSH Lifting Equation | RWL kg | NIOSH 94-110 | | calculateManualHandling | UK MAC manual handling risk | Green/Amber/Red | HSE UK MAC tool |

Environmental

| Function | Measures | Regulation | |---|---|---| | calculateWBGT | Wet Bulb Globe Temperature (heat stress) | ACGIH TLV / ISO 7243 | | calculateHeatIndex | NWS heat index (feels-like temp) | NWS / OSHA campaign | | calculateLuxLevel | Required workplace illuminance | CIBSE / EN 12464-1 | | calculateVentilation | Required ventilation rate (ACH) | ASHRAE 62.1 | | calculateCarbonFootprint | Scope 1+2+3 CO₂e | GHG Protocol |

Fire safety

| Function | Measures | Source | |---|---|---| | calculateFireLoad | Fire load density (MJ/m²) | NFPA 557 / BS 9999 | | calculateEvacuationTime | Required Safe Egress Time (RSET) | NFPA 101 / BS 9999 | | calculateFireExtinguisherSize | Minimum extinguisher rating | NFPA 10 / BS 5306 |

Workload & productivity

| Function | Measures | |---|---| | calculateManhours | Total exposure hours across shifts | | calculateFTE | Full-time equivalent workers |

Risk scoring

| Function | Measures | Output | |---|---|---| | calculateRiskMatrix | 5×5 or 4×4 risk matrix | score + L/M/H/E band | | calculateRiskReduction | Pre-control vs post-control residual | % reduction | | calculateSafetyScore | Composite safety performance KPI | 0-100 | | calculateStressRisk | HSE UK Stress Management Standards | 1-5 |

Incident rate formulas

calculateTRIR

OSHA Total Recordable Incident Rate — the single most requested HSE metric in the US. Required for OSHA 300A annual summary submission (29 CFR 1904) and used in insurance Experience Modification Rate (EMR) calculations.

calculateTRIR({ recordableIncidents: 3, hoursWorked: 500_000 });
// → { rate: 1.2, base: 200_000, formula: "(3 × 200,000) ÷ 500,000" }

Formula: TRIR = (Recordable Incidents × 200,000) ÷ Total Hours Worked

The 200,000-hour base represents 100 full-time equivalent workers × 40 hours/week × 50 weeks/year. A TRIR below 3.0 is considered good; below 1.0 is world-class.

calculateLTIR

OSHA Lost Time Incident Rate — counts only cases where the worker lost one or more full days away from work. A subset of TRIR.

calculateLTIR({ lostTimeIncidents: 2, hoursWorked: 500_000 });
// → { rate: 0.8, base: 200_000, formula: "(2 × 200,000) ÷ 500,000" }

Formula: LTIR = (Lost Time Incidents × 200,000) ÷ Total Hours Worked

calculateLTIFR

ISO/ILO Lost Time Injury Frequency Rate — international (non-US) standard. Uses 1,000,000-hour base. Required by ISO 45001:2018 for management review.

calculateLTIFR({ lostTimeInjuries: 3, hoursWorked: 500_000 });
// → { rate: 6, base: 1_000_000, formula: "(3 × 1,000,000) ÷ 500,000" }

Formula: LTIFR = (Lost Time Injuries × 1,000,000) ÷ Total Hours Worked

Used by HSE UK, IOGP, GCC countries (UAE, Saudi Arabia, Qatar, Kuwait, Oman, Bahrain), and most global safety frameworks.

calculateDART

OSHA Days Away, Restricted, Transferred rate. Used in BLS SOII benchmarking and OSHA VPP (Voluntary Protection Programs) evaluation.

calculateDART({ dartCases: 2, hoursWorked: 500_000 });
// → { rate: 0.8, base: 200_000, formula: "(2 × 200,000) ÷ 500,000" }

Formula: DART = (DART Cases × 200,000) ÷ Total Hours Worked

calculateSeverityRate

Severity rate — days lost per exposure base. Both OSHA (200k) and ILO (1M) bases supported.

calculateSeverityRate({ daysLost: 45, hoursWorked: 500_000, base: "iso" });
// → { rate: 90, base: 1_000_000 }

calculateFrequencyRate

International accident frequency rate — used by HSE UK, IOGP, ADNOC, Aramco, QatarEnergy.

calculateFrequencyRate({ accidents: 5, hoursWorked: 2_000_000 });
// → { rate: 2.5, base: 1_000_000 }

calculateEMR

Experience Modification Rate — multiplier applied to workers' compensation insurance premiums. An EMR of 1.0 is industry baseline; below 1.0 saves money; above 1.0 costs more.

calculateEMR({ actualLosses: 150_000, expectedLosses: 200_000 });
// → { emr: 0.75, savingsVsBaseline: "25%" }

calculateIncidentCost

Direct + indirect cost model based on OSHA $afety Pays tool. Indirect costs (investigation, lost productivity, training replacement) typically run 1.1× to 4.5× the direct cost depending on injury severity.

calculateIncidentCost({ directCost: 10_000, severity: "medical" });
// → { direct: 10_000, indirect: 11_000, total: 21_000, revenueNeeded: 210_000 }

Revenue-needed is calculated at a default 10% profit margin — the sales revenue required to cover the incident cost.

Occupational exposure

calculateWBGT

Wet Bulb Globe Temperature — the gold standard heat stress metric. Returns WBGT in °C plus ACGIH TLV-based work/rest ratio recommendations.

calculateWBGT({ tempC: 38, humidity: 60, globeTempC: 42, indoor: false });
// → { wbgt: 34.1, riskLevel: "high", acgihWorkRestRatio: "25/75" }

Formulas:

• Outdoor (with sun): WBGT = 0.7·Tw + 0.2·Tg + 0.1·Td
• Indoor (no sun): WBGT = 0.7·Tw + 0.3·Tg

Where Tw = natural wet bulb, Tg = globe temperature, Td = dry bulb. Critical in GCC summers, Australian mining, African construction.

calculateNoiseDose

OSHA 8-hour noise dose per 29 CFR 1910.95. Exchange rate: 5 dB (OSHA) or 3 dB (ACGIH / EU 2003/10/EC).

calculateNoiseDose({ leq: 92, hours: 8, exchangeRate: 5 });
// → { dose: 200, twa8h: 92, actionLevelExceeded: true, permissibleExceeded: false }

calculateHAV

Hand-Arm Vibration daily exposure A(8) per HSE UK L140. Action value: 2.5 m/s²; exposure limit: 5.0 m/s².

calculateHAV({ vibrationMs2: 4.2, exposureHours: 3 });
// → { a8: 2.57, actionExceeded: true, limitExceeded: false }

calculateWBV

Whole-Body Vibration per ISO 2631-1 / EU 2002/44/EC. Critical for haulage, excavator operation, forklift drivers.

Ergonomics

calculateREBA

Rapid Entire Body Assessment — Hignett & McAtamney 2000. Full-body ergonomic risk scoring for manual handling, construction, healthcare.

calculateREBA({
  neck: 2, trunk: 3, legs: 1,
  upperArm: 3, lowerArm: 2, wrist: 2,
  load: "medium", coupling: "fair", activity: "repeated"
});
// → { score: 7, risk: "medium", action: "further investigation required" }

calculateRULA

Rapid Upper Limb Assessment — McAtamney & Corlett 1993. Focus on neck, trunk, upper limbs for office, assembly, inspection work.

calculateNIOSHLift

NIOSH Lifting Equation (1994 revision). Calculates Recommended Weight Limit (RWL) and Lifting Index (LI) for manual lifting tasks.

Environmental

calculateLuxLevel

Required workplace illuminance per CIBSE and EN 12464-1. Office: 500 lx. Warehouse: 200 lx. Precision assembly: 1000 lx.

calculateVentilation

Required ventilation rate in air changes per hour (ACH) per ASHRAE 62.1.

calculateCarbonFootprint

Scope 1 (direct emissions) + Scope 2 (purchased energy) + Scope 3 (value chain) CO₂-equivalent in kg, per GHG Protocol and ISO 14064-1.

Fire safety

calculateFireLoad

Fire load density (MJ/m²) per NFPA 557 and BS 9999. Classifies as low (<800), moderate (<1,600), high (<3,200), very high (>3,200).

calculateEvacuationTime

Required Safe Egress Time (RSET) per NFPA 101 and BS 9999. Combines pre-movement time + travel time + flow time through exits.

calculateFireExtinguisherSize

Minimum extinguisher rating based on hazard class and floor area per NFPA 10 and BS 5306.

Workload & productivity

calculateManhours

Total exposure hours across multiple shifts, with support for overtime multipliers.

calculateManhours({ workers: 150, hoursPerDay: 10, days: 22, overtimePct: 15 });
// → { regular: 33_000, overtime: 4_950, total: 37_950 }

calculateWorkingDaysLost

Total productive days lost to injuries — required KPI for ISO 45001:2018 Clause 9.1 monitoring.

Risk scoring

calculateRiskMatrix

5×5 or 4×4 risk matrix scoring. Common in oil & gas (Aramco SAIC-SS, ADNOC, QatarEnergy), construction, and ISO 45001 risk registers.

calculateRiskMatrix({ likelihood: 4, severity: 5, matrix: "5x5" });
// → { score: 20, band: "extreme", color: "#DC2626", action: "stop work, elevate to leadership" }

Regulation citations

Every formula in this library is rooted in a published regulation or peer-reviewed ergonomic standard. No proprietary calculations, no "SmartQHSE recommends" values.

United States

• 29 CFR 1904.7 — OSHA recordability (TRIR, LTIR, DART)
• 29 CFR 1910.95 — OSHA occupational noise exposure
• NIOSH Publication 94-110 — Revised lifting equation
• NFPA 10, 101, 557 — Fire codes
• ASHRAE 62.1 — Ventilation
• NCCI — Workers comp EMR

United Kingdom

• HSE L140 — Hand-arm vibration
• HSE EH40 — Workplace exposure limits
• HSE MAC tool — Manual handling assessment charts
• BS 5306, BS 9999 — Fire safety
• HSE Stress Management Standards
• RIDDOR (Reporting of Injuries, Diseases and Dangerous Occurrences Regulations) 2013

International

• ISO 45001:2018 — OH&S management systems
• ISO 14001:2015 — Environmental management systems
• ISO 14064-1 — GHG quantification
• ISO 2631-1 — Whole-body vibration
• ISO 7243 — WBGT heat stress
• ILO — International Labour Organization frequency rate standards

Europe

• EU Directive 2003/10/EC — Noise
• EU Directive 2002/44/EC — Vibration
• EN 12464-1 — Workplace lighting

Professional bodies

• ACGIH TLVs® — Threshold Limit Values
• GHG Protocol — Scope 1/2/3 accounting
• IOGP — International Association of Oil & Gas Producers
• NIOSH — National Institute for Occupational Safety and Health

Who uses this library?

• EHS / HSE managers running monthly KPI dashboards
• Construction project safety teams calculating TRIR for Aramco / ADNOC / QatarEnergy / Procore prequalification
• ISO 45001 consultants generating compliant metric outputs for Clause 9.1 monitoring
• Occupational hygienists quantifying noise, vibration, chemical, and heat exposure
• Ergonomists documenting REBA, RULA, NIOSH assessments
• Insurance brokers estimating EMR impact of incident reduction programs
• Safety software vendors embedding calculation engines into their products
• Universities teaching occupational health and safety courses
• Governments publishing national HSE benchmarks

Need the full platform?

SmartQHSE is the AI-powered HSE / QHSE management platform built on top of these calculators.

| Feature | This library | SmartQHSE platform | |---|---|---| | 30+ HSE calculators | ✅ | ✅ (+ UI) | | AI-generated risk assessments | ❌ | ✅ (ARIA) | | AI-generated method statements, JSAs, toolbox talks | ❌ | ✅ | | Permit-to-Work (PTW) workflow with signatures | ❌ | ✅ | | Incident Management + RCA | ❌ | ✅ | | Contractor prequalification | ❌ | ✅ | | ISO 45001 / 14001 / 9001 compliance dashboards | ❌ | ✅ | | Real-time KPI tracking against these calculators | ❌ | ✅ | | Regional compliance (OSHAD, Aramco, QatarEnergy, SABIC) | ❌ | ✅ | | Arabic bilingual | ❌ | ✅ |

Start free: smartqhse.com · Pricing: from $49/mo · Demo: smartqhse.com/how-it-works

Contributing

We welcome contributions — new calculators, improved formulas, additional regulation citations, translations. See CONTRIBUTING.md.

License

MIT © SmartQHSE Ltd — see LICENSE.

If you use these calculators in production software, a backlink to smartqhse.com is appreciated but not required.

Related resources

• SmartQHSE Safety Blog — smartqhse.com/safety-blog (244+ articles on OSHA, ISO 45001, HSE best practices)
• HSE Glossary — smartqhse.com/hse-glossary
• Regulations index — smartqhse.com/regulations
• ISO 45001 implementation guide — smartqhse.com/iso-45001-implementation-guide
• Best HSE software 2026 — smartqhse.com/best-hse-software-2026

Keywords

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