DART rate calculator

Hours worked of zero make that ratio undefined, so the task fails with invalid_input instead of inventing a rate. Use it free in the browser, or call the API at $0.002 per successful item for dashboards, bid packages, and year-end OSHA summaries that must see the same figure every time.

What the DART rate measures and what the response contains

DART stands for Days Away, Restricted, or Transferred. On the OSHA 300 log those are the recordable cases in columns H and I: someone missed work, was put on restricted duty, or was transferred because of a work-related injury or illness. The DART rate scales that count to one hundred full-time equivalent workers so a fifty-person shop and a two-thousand-person plant can be compared without the larger site always looking worse. The identity is dart_rate equals days_away_cases times 200000 divided by hours_worked. The companion incident_rate, often called TRIR, uses the same baseline on recordable_incidents instead of DART cases. equivalent_workers is hours_worked divided by 2000, the conventional hours of one full-time employee over a year, so a reviewer can see the size of the exposed population behind the rate. When recordable_incidents is greater than zero, dart_share_percent is the share of recordables that became DART cases; a high share means the recordables that did occur were serious enough to take people off ordinary duty. Zero recordable incidents with zero DART cases is a legal year: both rates are zero and dart_share_percent is omitted rather than printed as null. This calculator does not classify a case as recordable, does not count calendar days lost, and does not apply a 1,000,000-hour lost-time convention used in some industrial standards. It either scales three finite numbers inside the supported range or rejects the input with invalid_input. Rejected cases include missing fields, non-finite values, magnitudes above the documented ceiling, a negative count, DART cases that exceed recordables, and any hours_worked value that is zero or negative, because division by zero is undefined and a non-positive hour total does not define incidents per 100 workers.

Input contract, aliases, and how the quotient stays reproducible

Fractional hours are accepted because payroll systems emit tenths; case counts may be whole logs or year-to-date estimates. POST a JSON body with three required finite numbers: recordable_incidents, days_away_cases, and hours_worked. recordable_incidents is the OSHA recordable count for the window, a number that is not negative, with aliases recordable, incidents, total_recordable, recordables, and n. days_away_cases is the DART numerator for that same window, a number that is not negative and must not exceed recordable_incidents, with aliases dart_cases, days_away, dart, dart_incidents, and dafw. hours_worked is total hours actually worked by all employees in that window, a number strictly greater than zero, with aliases hours, total_hours, eh, exposure_hours, and employee_hours. Each field may arrive as a JSON number or as a numeric string; optional leading plus signs and scientific notation are allowed when they parse as finite decimals. Empty strings, missing fields, and non-numeric tokens fail with invalid_input naming the field and are not billed. The error this landing exists to catch is hours_worked of zero: the message contains hours worked are zero so a form can highlight that control instead of a generic alert. Pair the free browser run on this page with the priced API when a bid desk, insurer portal, or nightly EHS script must see the identical OSHA identity without re-implementing the 200,000-hour baseline in a spreadsheet that silently changes the decimal separator.

Where a DART rate calculator earns its keep

People meet the DART rate when a safety manager closes the OSHA 300A, when a general contractor asks a subcontractor for last year's rate before issuing a gate pass, when an insurer prices workers compensation, or when a corporate EHS dashboard flags a site whose DART moved while headcount barely changed. Bid packages for construction and manufacturing often demand both the recordable incident rate and the DART rate so a buyer can see not only how many cases occurred but how many took people off ordinary duty. Homework and professional-certification drills need a fast, offline source of the 200,000-hour identity so solutions can be checked without opaque macros under time pressure. Growth and operations engineers call the same contract from scripts to seed deterministic test vectors for EHS dashboards, to normalize user-entered log counts before a demo, or to satisfy a product challenge that demands a dart_rate field rather than a hand-waved safety claim. This identity is not a substitute for incident investigation, root-cause analysis, or a medical-only versus restricted-duty classification on the log itself, but it is the number every OSHA 300A already implies next to hours worked. On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split — free interactive exploration and a priced, identical API — matches the rest of the tier-A catalog and lets you move from a classroom demo to an automated year-end summary without changing the mathematical result. Pair it with other finance and operations endpoints when you are building a small lab of free, deterministic rate helpers that stay honest about the baseline they scale.