Calculator
% Sick units calculator
Sick units are equipment that fail repeatedly within a short window. Set the criteria (by default, 3 or more failures in 30 calendar days), count how many units meet them and compare with the total fleet.
Result
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Reference ranges are indicative and vary by industry, asset type and operating regime. Nothing you type leaves your browser.
What is a sick unit
It's a piece of equipment that keeps failing within a short interval. The most common criterion is 3 or more failures in 30 calendar days, counted over a rolling window: an elevator that fails on Sep 28, Oct 5 and Oct 20 qualifies, even though the failures fall in different months.
The metric shows concentration: in many fleets, a few units generate a large slice of service calls. Reducing sick units usually cuts corrective work volume faster than any other action.
Common mistakes
Counting preventive visits as failures, logging the same incident twice and changing the criteria from one month to the next, which makes it impossible to compare the trend.
To tackle each one: 5 whys in maintenance.
Frequently asked questions
What are sick units?
Equipment with recurring failures within a short window. The most widely used criterion is 3 or more failures in 30 calendar days.
How do you calculate % sick units?
% sick units = units that met the criteria ÷ total units in the fleet × 100.
Why use a rolling window of calendar days?
Because failures at the end of one month and the start of the next are recurring too. The calendar month hides these cases.
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