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Severity Rate Calculator

Work out severity rate instantly with clear inputs, formula shown and shareable results.

About Severity Rate Calculator

Severity rate normalises days lost rather than injury count, so it captures how serious the injuries were rather than how many occurred. Read alongside frequency rate it distinguishes a site with many minor injuries from one with few but disabling ones, and average days per injury is the ratio between the two.

Formulas

Severity rate

Rate = days lost x base hours / hours worked

Average severity

Days per injury = days lost / lost time injuries

Worked example

With the default values below, Severity Rate Calculator returns Severity rate of 168.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Days lostminimum 0 days
84 days
Lost time injuriesminimum 0
3
Hours workedminimum 1 h
500,000 h
Base hours for the rateminimum 1 h
1,000,000 h

Results

Severity rate
168.00
Average days lost per injury
28.00 days
Lost time injury frequency rate
6.000
Days lost per 200,000 hours
33.60

Step by step

  1. 1Values used
  2. 2Severity rate
  3. 3Average severity
  4. 4Severity rate= 168.00
  5. 5Average days lost per injury= 28.00 days
  6. 6Lost time injury frequency rate= 6.000
  7. 7Days lost per 200,000 hours= 33.60

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Severity Rate figure worked out?

Rate = days lost x base hours / hours worked. Severity rate normalises days lost rather than injury count, so it captures how serious the injuries were rather than how many occurred.

Should fatalities be counted in days lost?

Conventionally a fatality or permanent total disability is charged at 6000 days so that severe outcomes dominate the statistic as they should. Practice varies, so the basis must be stated.

What values do I need to enter?

This calculator takes 4 inputs: Days lost, Lost time injuries, Hours worked, Base hours for the rate. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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