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Downtime: What It Means, Planned vs Unplanned and How it Differs from Idle Time

Downtime is any period when equipment that should be running is not. It splits into planned downtime, which you schedule for maintenance or changeovers, and unplanned downtime, the breakdown nobody wanted. People also confuse it with idle time, when the machine is ready but has no work to do.

Why does downtime matter?

Downtime is one of the largest and most controllable losses in any plant, because every stopped minute is output you still pay for in labor and overhead. Left unmeasured, the same faults keep recurring, maintenance stays reactive, and both reliability and throughput slowly erode. Tracking downtime is what turns those hidden losses into a clear list of problems worth fixing.

What counts as planned and unplanned downtime?

The split matters because you manage the two in completely different ways:
  • Planned downtime is on the calendar: preventive maintenance, a tool change, a scheduled clean.
  • Unplanned downtime is the surprise: a breakdown, a jam, a fault that trips the line mid-run.
  • You reduce planned downtime by working more efficiently, and reduce unplanned downtime by fixing the root cause.
  • Both count against availability, so both belong in the same log. 

How is downtime different from idle time ?

The difference is the machine’s readiness. Downtime means the equipment cannot run: it is broken, in maintenance, or waiting on a fix. Idle time means the equipment is able to run but has nothing to do, usually a starved feed or a bottleneck upstream. Downtime is an equipment problem; idle time is a flow problem, and the fixes rarely overlap.

Why is downtime worth tracking to the minute? 

Unmeasured downtime hides the real losses. Log every stop with a cause and you can see which failures cause the most lost hours, which feeds machine availability and the availability leg of OEE. A stop you never recorded is a stop you will pay for again.

Downtime vs idle time at a glance

The two states people log as the same thing, separated. 

AspectDowntimeIdle Time
Can the machine run?NoYes
Typical causeBreakdown, maintenance, faultNo work, starved feed, bottleneck
OwnerMaintenancePlanning / scheduling
FixRepair, prevent recurrenceBalance the flow, feed the line
HitsAvailabilityUtilization

Free downtime log  

It records every stop with its start, end, cause and the action taken, so your biggest losses become visible. Download the checklist (PDF). You can also complete the checklist digitally in flowdit on your phone, tablet or PC.

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