---
title: "Planned vs unplanned downtime and what counts against OEE"
description: "Breaks, changeovers and planned maintenance are all downtime. See which count against OEE availability, with one shift worked three ways and a decision table."
category: "Downtime and utilization"
author: "Ulises Carrasco"
published: "2024-05-03"
updated: "2026-10-20"
source_url: "https://www.iotflows.com/blog/planned-vs-unplanned-downtime/"
---
> Question: Do breaks, changeovers and planned maintenance count as downtime, and do they count against availability?

## Key takeaways

- Breaks, changeovers and planned maintenance are all downtime, because the machine is stopped and makes no parts.
- Planned or unplanned says whether you chose a stop; whether the machine was meant to run decides availability.
- Under the common OEE convention, idle breaks leave planned production time, while changeovers and in-shift maintenance stay in as losses.
- The same shift can read 71.9%, 76.7% or 88.5% availability, depending on which stops leave the denominator.
- Write your convention under every OEE report, and compare plants only when they draw the line in the same place.

Breaks, changeovers and planned maintenance all count as downtime, because the machine is stopped, but they don’t all count against availability. Under the common OEE convention, a break with nobody meant to run the machine comes out of planned production time first. A changeover or a maintenance job inside a scheduled shift stays in and lowers availability, even though you planned it.

One test decides where each stop goes, and a decision table applies it to the stops plants argue about. One shift on a molding press, worked three ways, shows how far the convention moves the number.

## Planned vs unplanned downtime

> **Definition.** **Planned downtime** is a stop decided before it happened and written into the schedule, such as a changeover, a preventive maintenance job or a lunch break. The machine is stopped and makes no parts, so planned downtime is still downtime.

> **Definition.** **Unplanned downtime** is a stop the schedule did not account for, such as a breakdown, a broken tool, a jam, a missing operator or material that did not arrive. It also covers the part of a planned job that runs past its scheduled slot.

NIST’s maintenance survey report puts the first point in one line: “PM is planned downtime which is still downtime.”[3] The [planned downtime glossary entry](/docs/get-started/glossary/#planned-downtime) shows how IoTFlows marks those stops.

Planned or unplanned answers one question: did you choose this stop? Availability asks a different one: was the machine meant to be making parts at the time? Keep the two questions apart and most arguments about planned time settle quickly.

## What counts against availability?

*Availability* is run time divided by planned production time. *Planned production time* is the shift minus any time with no intention of running production, and Vorne’s OEE primer names breaks as the usual example.[1]

**Availability** = (Run time) ÷ (Planned production time)

*Stop time* is the rest of the time the machine was meant to run and didn’t. It includes unplanned stops, such as breakdowns, and planned stops, such as changeovers.[1] The six big losses file planned stops under setup and adjustments, an availability loss: setups, changeovers, cleaning, warm-up, planned maintenance and quality inspections.[2]

That leaves one test. Take time out of planned production time only when nobody intended to run the machine. Keep it in when the machine was scheduled to run and didn’t, whatever the reason and whoever chose it.

Figure: A 480-minute shift on a molding press: 345 minutes running, a 30-minute lunch outside planned production time, a 45-minute mold change and 15-minute PM counted as planned stops, and 45 minutes of unplanned stops. Availability is 345 ÷ 450 = 76.7%.

*Lunch leaves planned production time; the mold change and the PM stay in, next to the breakdown. Sample data.*

For example, the press above runs a 480-minute day shift with a 30-minute lunch, so planned production time is 450 minutes. The mold change and the lubrication PM were both on the schedule, and both stay in. The guide to [calculating OEE from one shift](/blog/how-to-calculate-oee/) carries the same structure through performance and quality.

## Where each stop goes

The table covers ten stops that plants argue about. Read each row with the one test: was the machine meant to run?

| Stop | Planned? | In availability? | Why |
|---|---|---|---|
| Lunch with the machine left idle | Yes | No | Nobody meant to run it |
| Covered lunch, relief operator absent | No | Yes | The machine was meant to run |
| Changeover on the schedule | Yes | Yes | It takes scheduled run time |
| Changeover swapped in for a rush job | No | Yes | It was not on the schedule |
| Changeover running past its slot | Slot yes, overrun no | Yes | Split the record in two |
| PM during a scheduled shift | Yes | Yes | It takes scheduled run time |
| PM on a weekend with no shift | Yes | No | No production was planned |
| Breakdown or broken tool | No | Yes | The classic availability loss |
| Waiting for material or an operator | No | Yes | Machine ready, nothing to run |
| No orders, machine scheduled off | Yes | No | Outside planned production time |

Convention from Vorne’s OEE primer and six big losses. Your plant decides what counts as planned production time, so write it down.

### Breaks and meetings

A break comes out only when the machine sits idle by plan. If a relief operator is meant to cover lunch, the machine was scheduled to run, and every stop in that slot is unplanned downtime.

A 10-minute shift-start meeting follows the same test. Take it out when the machine is meant to sit through it, and keep it in when the machine was meant to run.

### Changeovers

A changeover written into the schedule is planned and still counts. Vorne calls changeovers the usual largest source of setup and adjustment time,[2] so taking them out of the denominator hides the loss you most want to shrink.

A changeover swapped in mid-shift for a rush job is unplanned. When you have to think about whether a stop was scheduled, it was not.

### Planned maintenance

Preventive maintenance inside a scheduled shift is a planned stop, and it lowers availability. The same job moved to a Saturday with no shift sits outside planned production time, so it costs OEE nothing.

That’s a reason to move PM into non-production hours where your plant has them. It isn’t a reason to relabel in-shift PM as excluded time.

### Overruns

A 45-minute mold change that takes 70 minutes is two records: 45 planned minutes and 25 unplanned ones. Both stay in availability. The split tells you whether the plan was too tight or the changeover went wrong.

## Work one shift three ways

The convention is a choice, and on one shift it moves availability by 16.6 points. Here is the shift from the figure above, with three different denominators.

#### Worked example: One 8-hour shift on a 350-ton molding press

- Shift: 06:00 to 14:00, 480 minutes, with a 30-minute lunch and the press left idle.
- Planned stops: a 45-minute mold change and a 15-minute lubrication PM, 60 minutes in all.
- Unplanned stops: a 30-minute heater band failure and 15 minutes waiting for resin, 45 minutes in all.
- Run time: 480 − 30 − 60 − 45 = 345 minutes.

| Convention | Denominator | Availability |
|---|---|---|
| Whole shift | 480 min | 345 ÷ 480 = 71.9% |
| Breaks out | 450 min | 345 ÷ 450 = 76.7% |
| Breaks and planned stops out | 390 min | 345 ÷ 390 = 88.5% |

**Result:** The same 345 run minutes read anywhere from 71.9% to 88.5% availability.

Figure: Three availability bars for the same 345 run minutes: 71.9% over the whole 480-minute shift, 76.7% with breaks removed (450 minutes), and 88.5% with breaks and planned stops removed (390 minutes).

*One shift, three denominators: a 16.6-point spread with no change on the floor. Sample data.*

The middle row follows the common OEE convention. The bottom row answers a different question, how much of the time you meant to produce went to stops nobody chose, and it isn’t OEE availability.

That reliability question has its own ratio: unplanned downtime as a share of planned production time. NIST’s survey of US discrete manufacturers asked for exactly this, and the average answer was 7.8%.[3] On this press it’s 45 ÷ 450 = 10.0%.

Standards don’t settle the line either. ISO 22400 gives two definitions of OEE, and a 2020 review found they seem to diverge from each other and from Nakajima’s original TPM formulation.[4] SEMI E10, written for the semiconductor and related industries, defines six mutually exclusive equipment states and names unscheduled downtime as the failed one.[6]

Hours with no shift belong to a different metric. TEEP multiplies OEE by utilization, planned production time over all time, so it is the one that counts the weekend.[5] The guide to [utilization, OEE and TEEP on one calendar](/blog/utilization-uptime-oee-teep/) lines these metrics up hour by hour.

> **Compare plants on one convention**
>
> Before you compare two plants’ availability, check what each removes from planned production time. A plant that removes changeovers reports 88.5% for the same shift another plant reports as 76.7%, and neither number is wrong.

## Why keep planned stops in availability?

Planned stops cost the same minutes as unplanned ones. A 45-minute mold change is 45 minutes the press made no parts, whether you scheduled it or not. Keeping planned stops in the denominator keeps them on the list of losses you work on.

[Datwyler’s injection molding plant](/customers/datwyler/) shows why. With a reason on every stop, it cut shift-changeover downtime in half and material-changeover downtime by 30% within six months. Both are stops a plant plans for, and both gains would be invisible on an availability figure that left them out.

> **Which basis should you report?**
>
> Report availability with idle breaks out and every other stop in when you track OEE, set goals or compare machines. Report unplanned downtime as a share of planned production time when the maintenance team needs a reliability number. You don’t need a third basis that removes planned stops from availability: it raises the number without saving a minute.

## Track planned and unplanned stops automatically

IoTFlows detects every stop from a sensor on the machine, with no PLC connection, and sorts it into the shift it fell in. Set your [shifts and timezone](/docs/admin/shifts-and-timezone/) first, since they decide which hours count at all.

Mark each downtime category planned or unplanned once, with the **Planned downtime** toggle. Operators then see a calendar icon on planned reasons when they classify a stop, and changeovers and maintenance rank by hours next to breakdowns.

A [scheduled break window](/docs/monitoring/auto-downtime-rules/#breaks) classifies every stop in your lunch slot automatically. Give that break category the [None severity](/docs/monitoring/metrics-reference/#none), and **Exclude None** on the Advanced Report takes it out of both uptime and downtime, matching the convention above. See how [downtime tracking](/solutions/downtime-tracking/) works.

## Set your plant’s convention

1. **List what leaves planned production time.** Write down every kind of time with no plan to run: unstaffed breaks, hours with no shift and days with no orders. Everything else stays in.
2. **Flag every reason code.** Mark each reason planned or unplanned when you build the list, then set its severity separately. The [starter list of reason codes](/blog/downtime-reason-codes/#starter-list) shows both settings on every code.
3. **Split overruns from the plan.** Record a changeover’s scheduled minutes as planned and the rest as unplanned. Cut the stop record in two at the end of the scheduled slot and give each half its own reason.
4. **Print the convention on the report.** Put one line under every OEE number saying what came out of planned production time. A reader in another plant can then compare like with like.
5. **Shrink the planned stops too.** Rank planned stops by hours next to breakdowns and start on the largest. [Measure changeover time](/blog/measure-changeover-time/) before you try to cut it.

## Questions

### Is a lunch break counted as downtime?

On the machine, yes: it is stopped, and a sensor records the stop. In OEE, a lunch with the machine left idle comes out of planned production time, so it lowers neither availability nor OEE. If a relief operator is meant to keep the machine running through lunch, any stop in that slot is unplanned downtime and counts against availability.

### Does a changeover that runs long count as planned downtime?

Only the scheduled part. Record the minutes the schedule allowed under a planned changeover reason and the overrun under an unplanned reason, such as waiting for a mold or a failed first article. Both parts still lower availability, and the split shows whether the plan was too tight or the changeover went wrong.

### Does maintenance done on a weekend lower OEE?

No, when no production shift is scheduled that weekend. OEE measures only planned production time, so hours with no plan to run sit outside it. TEEP divides by every hour on the calendar, but it already counts those weekend hours as unscheduled, so maintenance in them lowers TEEP no further. Maintenance inside a scheduled shift lowers both.

### Why do some plants report availability with planned stops removed?

Removing changeovers and planned maintenance from the denominator isolates the stops nobody chose, which suits a maintenance team tracking breakdowns. The cost is a higher number that hides capacity lost to setups. Report that view under its own name, such as unplanned downtime as a share of planned production time, rather than calling it OEE availability.

## Sources

1. [OEE Calculation: Definitions, Formulas, and Examples](https://www.oee.com/calculating-oee/), Vorne Industries, accessed Oct 16, 2026
2. [Six Big Losses in Manufacturing](https://www.oee.com/oee-six-big-losses/), Vorne Industries, accessed Oct 16, 2026
3. [Economics of Manufacturing Machinery Maintenance: A Survey and Analysis of U.S. Costs and Benefits (NIST AMS 100-34)](https://nvlpubs.nist.gov/nistpubs/ams/NIST.AMS.100-34.pdf), National Institute of Standards and Technology, accessed Oct 16, 2026
4. [Overall Equipment Effectiveness: consistency of ISO standard with literature (Schiraldi and Varisco, Computers & Industrial Engineering 145, 2020)](https://art.torvergata.it/handle/2108/280082), University of Rome Tor Vergata institutional repository, accessed Oct 16, 2026
5. [TEEP: Total Effective Equipment Performance](https://www.oee.com/teep/), Vorne Industries, accessed Oct 16, 2026
6. [SEMI E10: Specification for Definition and Measurement of Equipment Reliability, Availability, and Maintainability (RAM) and Utilization](https://store-us.semi.org/products/e01000-semi-e10-specification-for-definition-and-measurement-of-equipment-reliability-availability-and-maintainability-ram-and-utilization), SEMI, accessed Oct 16, 2026