How to calculate TRIR
Choose matching cases and hours and interpret a worked example.
Open related tool ↗LEARN THE METHOD · 20 GUIDES
Understand the inputs.
Make sense of the result.
Choose the subject you need. Each guide explains the tool's scope, input choices, example and interpretation limits.
Incident rates
How to calculate DART rate
Count cases rather than days and compare DART with TRIR.
Open related tool ↗Calculate LTIFR with consistent lost-time case definitions
Calculate lost-time injury frequency rate from lost-time injury cases and actual employee hours.
Open related tool ↗Calculate injury frequency rate on a million-hour basis
Calculate a frequency rate for new occupational injury cases using a fixed one-million-hour basis.
Open related tool ↗Calculate lost-workday severity rate and check the reporting base
Calculate recorded lost workdays per 1,000 hours worked, with the reporting basis clearly stated.
Open related tool ↗Heat exposure
Understand WBGT inputs before interpreting heat exposure
Combine measured heat sensors without confusing WBGT with air temperature.
Open related tool ↗Noise exposure
Calculate daily noise exposure from multiple tasks
Combine task noise readings into an eight-hour energy-normalised daily exposure.
Open related tool ↗Safety briefings
Prepare a toolbox talk that leads to clear actions
Prepare a focused site briefing with practical actions and a usable record.
Open related tool ↗Ergonomics
Use the NIOSH origin lifting worksheet with verified multipliers
Calculate an origin recommended weight limit and lifting index using measured geometry and verified multipliers.
Open related tool ↗Fire protection
Plan extinguisher quantities using assessed coverage inputs
Estimate quantities across identical zones using a coverage value supplied by your fire assessor.
Open related tool ↗Workforce planning
How to calculate man-hours without double-counting
Total worked or planned person-hours for a group with the same schedule.
Open related tool ↗Convert man-hours to man-days on a stated basis
Convert total person-hours into equivalent person-days using your chosen hours-per-day definition.
Open related tool ↗Lifting operations
Calculate equal two-leg sling tension using the horizontal angle
Estimate tension in each of two equal sling legs, with the angle measured from horizontal.
Open related tool ↗Work at height
Estimate leaning-ladder length using the UK 1-in-4 rule
Estimate base offset and ladder length using four units vertically up for every one unit horizontally out.
Open related tool ↗Check fall-clearance inputs against the actual equipment method
Add the clearance components specified by your selected fall-arrest system and compare the sum with available clearance.
Open related tool ↗Chemical exposure
Calculate an eight-hour chemical TWA from exposure periods
Combine concentration readings and durations for one substance across a complete eight-hour period.
Open related tool ↗Vibration exposure
Work out daily hand-arm vibration A(8) and exposure points
Combine actual trigger times and representative vibration magnitudes for the tools used during a day.
Open related tool ↗Combine whole-body vibration readings by axis
Calculate daily x, y and z exposure from frequency-weighted RMS readings and find the highest daily axis.
Open related tool ↗Excavation planning
Calculate excavation top width from an assessed slope ratio
Work out the top width, horizontal run and angle of a symmetrical excavation from an assessed slope ratio.
Open related tool ↗Equipment protection
Read an IP rating without assuming it means waterproof
Understand the solid-object and water characters in an enclosure’s declared IP code.
Open related tool ↗Use the right source for the task
Some resources use GB or US methods. Others are plain arithmetic or equipment-specific worksheets. Check the scope before transferring a result to your work. Read how methods and sources are used.
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