The accident incident rate calculator UK on this page turns your injury counts and hours worked into the safety rates that GB employers actually report: the accident frequency rate (AFR), the lost time injury frequency rate (LTIFR), and the HSE incidence rate per 100,000 employees. Enter a handful of figures and it runs every calculation at once, then benchmarks your result against the latest Health and Safety Executive numbers.
Why bother standardising? A raw injury count means little until you set it against size and exposure. Two workplace accidents in a 20-person workshop tell a very different story from two across 2,000 staff. Frequency rates fix that, so you can track safety performance over time and measure it against your industry instead of guessing.
Accident Incident Rate Calculator UK
Work out every workplace safety rate that matters in Great Britain from one set of numbers: AFR per 100,000 hours, LTIFR per 1,000,000 hours, and the HSE incidence rate per 100,000 employees, benchmarked against the latest published GB figures. Flip one switch to see the same data in US OSHA terms (TRIR, DART) for group reporting.
Formulae follow the conventions HSE and OSHA publish: AFR = LTIs × 100,000 ÷ hours; LTIFR = LTIs × 1,000,000 ÷ hours; HSE incidence = injuries × 100,000 ÷ average employed; TRIR/DART = cases × 200,000 ÷ hours. GB benchmarks are from the HSE 2024/25 annual statistics (59,219 RIDDOR-reported employee injuries, 209 per 100,000 employees; 680,000 self-reported injuries, 2,070 per 100,000 workers; 124 worker fatalities, 0.37 per 100,000). HSE cautions that employers report only around half of RIDDOR-qualifying injuries, so cross-sector comparisons carry uncertainty. This tool does not determine what you must report under RIDDOR and is not legal advice; reporting duties are set out at hse.gov.uk/riddor.
What is the accident frequency rate?
The accident frequency rate is the number of lost time injuries per 100,000 hours worked. It is the headline metric UK health and safety teams use to show how often injuries happen relative to exposure, rather than as a bare total. A lower AFR means fewer injuries for every block of hours your workforce puts in.
The definition matters because an accident here is not every trip or near miss. For the AFR, an accident is usually a work-related injury that stops someone working beyond the day of the event, a lost time injury. Some firms count all accident-book entries instead. The calculator lets you decide, as long as you benchmark against a matching figure. That standardising step is what this accident frequency rate calculator automates.
The AFR formula and the rates it calculates
The AFR formula is: AFR = (number of lost time injuries × 100,000) ÷ total hours worked. To calculate AFR, multiply your lost time injuries by 100,000 and divide by the total hours worked in the period. That single calculation is the core of the tool, but it produces several related metrics from the same inputs.
- AFR: lost time injuries per 100,000 hours.
- LTIFR: the lost time injury frequency rate, the same injuries scaled per 1,000,000 hours, common in international and ISO reporting.
- HSE incidence rate: injuries per 100,000 employees, the basis for HSE’s published figures.
- TRIR and DART: the US OSHA metrics per 200,000 hours. TRIR is the total recordable incident rate, useful if you report to a US parent or client.
- Severity rate and average days lost per injury, from your total working days lost.
How to Use the Accident Incident Rate Calculator UK
Follow these steps. The AFR calculator updates as you type, so you can test different inputs.
- Pick your reporting convention. Leave it on UK / HSE for AFR, LTIFR and the incidence rate, or switch to US OSHA to see TRIR and DART instead.
- Enter your reportable injuries. For GB that means RIDDOR-reportable injuries. On the OSHA setting, enter total recordable cases from your 300 log.
- Enter lost time injuries (LTIs), the ones causing absence beyond the day of the event. This count drives the AFR and LTIFR.
- Add work-related fatalities and total working days lost. These feed the fatality rate, severity rate and average days per injury.
- Enter total hours worked across all staff for the period. Payroll is best; as a guide, a full-time GB employee works roughly 1,760 hours a year.
- Enter the average number employed so the tool can work out the incidence rate per 100,000 employees.
- Choose a benchmark and read your rates. Match the basis: the RIDDOR benchmark for RIDDOR counts, a self-reported figure for accident-book counts.
RIDDOR: what you actually have to report
RIDDOR stands for the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations. It sets out which workplace incidents a UK employer must report to the HSE: specified injuries, any injury that keeps a worker off normal duties for more than seven days, certain occupational diseases, and dangerous occurrences. Deciding what to feed the calculator starts with this regulation.
There is a catch. HSE estimates that only around half of qualifying injuries are actually reported, so a rate built purely on RIDDOR data understates real exposure. That is why the authority also publishes self-reported figures from the Labour Force Survey (LFS), and why the calculator offers both benchmarks. The tool does not decide what you must report; the reporting of injuries rules at hse.gov.uk/riddor do.
UK benchmarks: what a good AFR looks like
There is no universally good rate, but the HSE 2024/25 statistics give solid reference points. Across all industries, GB employers reported 209 RIDDOR injuries per 100,000 employees, while the Labour Force Survey put self-reported injuries at about 2,070 per 100,000 workers. Worker fatalities ran at 0.37 per 100,000, 124 in total.
Higher-risk sectors sit above the average. Construction, transport and storage, and manufacturing all report self-reported rates in the 2,100 to 2,500 per 100,000 range. Compare like with like: a rate built from every accident-book entry belongs against the self-reported figure, not the much lower RIDDOR one. The calculator flags whether you land above or below the benchmark you pick.
AFR vs LTIFR vs TRIR vs incidence rate
These metrics measure similar things with different denominators, which is why one workplace can quote several rates at once. Here is how they line up.
| Metric | What it counts | Normaliser | Typical use |
|---|---|---|---|
| AFR | Lost time injuries | per 100,000 hours | UK site and company reporting |
| LTIFR | Lost time injuries | per 1,000,000 hours | International and ISO reporting |
| TRIR | Total recordable cases | per 200,000 hours | US OSHA reporting |
| Incidence rate | Reportable injuries | per 100,000 employees | HSE published statistics |
The key point: never compare an AFR against a TRIR directly. The 100,000 versus 200,000 hour bases alone make TRIR look larger for the same injuries. Convert to a common metric first, which is what the tool does when you flip the convention switch.
Common mistakes when calculating incident rates
- Mixing the basis. Counting every workplace accident but benchmarking against RIDDOR-only figures makes your incident rate look alarming for no reason.
- Guessing total hours worked. Overtime in, annual leave out. A rough headcount times 1,760 is a start, but payroll data is far better.
- Redefining lost time mid-year, so your trend line measures your paperwork rather than your safety performance.
- Reading one year as a trend. On small headcounts a single extra injury swings the rate hard, so watch the direction over several periods.
Used consistently, the accident incident rate calculator UK gives you a defensible number for board reports, tenders and safety reviews, plus a fair way to compare this year with last. Treat the output as a management indicator, not a legal judgement: for what you must report, always check the current RIDDOR rules. For related tools, see our accident at work compensation calculator, accident claim calculator and accident probability calculator.
Frequently asked questions
How do you calculate the accident incident rate?
Divide the number of injuries by the total hours worked, then multiply by a standard number of hours. The UK AFR uses 100,000 hours: AFR = (lost time injuries × 100,000) ÷ total hours worked. The HSE incidence rate instead divides reportable injuries by the average number employed and multiplies by 100,000.
What is a good AFR rate?
There is no official threshold, but lower is better and context is everything. As a reference, GB employers reported 209 RIDDOR injuries per 100,000 employees in 2024/25 (HSE). Compare your figure with your own sector and your own past years rather than one national number.
What are RIDDOR reportable incidents in the UK?
Under RIDDOR, employers must report specified injuries (such as fractures other than to fingers or toes, amputations and serious burns), injuries that keep a worker off normal duties for more than seven days, certain occupational diseases, and dangerous occurrences. Full definitions sit on the HSE website.
What is the difference between LTIFR, TRIR and AFR?
All three are injury frequency rates; the difference is the injuries counted and the hours base. AFR and LTIFR both count lost time injuries but scale them per 100,000 and per 1,000,000 hours. TRIR counts all OSHA recordable incidents per 200,000 hours. Because the bases differ, convert before you compare.
What is the accident rate in the UK?
For 2024/25 the HSE reported 209 non-fatal injuries per 100,000 employees under RIDDOR, and the Labour Force Survey estimated about 2,070 self-reported injuries per 100,000 workers. Worker fatalities were 0.37 per 100,000, 124 in total.