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Wrench Time in Maintenance: Benchmarks and Formula

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Using the benchmarks

Wrench time measures the system, not the crew.

Wrench time is the share of a paid maintenance hour that a technician spends with hands on an asset, doing maintenance work. Walking, waiting, searching for parts, meetings, paperwork and travel do not count. In most plants it is far lower than managers expect, and almost all of the loss comes from planning, parts and scheduling, not from effort.

The wrench time formula and a worked shift.
Palmer's four benchmark tiers, with what a shop looks like at each one.
How to measure your own crew in one day.
The one-pager below, printable as a PDF.

The wrench time formula

Wrench time % = hands-on labor hours ÷ paid labor hours × 100

Count labor hours, not clock hours. Three mechanics on one bearing change for 2 hours and 50 minutes is 8.5 hands-on labor hours. Count only time with hands on an asset doing maintenance work. For a larger study across crews and shifts, use work sampling instead: random observations with tools on the job ÷ all observations × 100.

From the book: one Wednesday, one crew

Story from Fix the System, Chapter 1.

A maintenance manager followed one crew for a full shift and logged every minute. The morning huddle ran long. The bearing had been pulled from the kit for another job, so an apprentice walked the plant to find one. The line could not stop until the supervisor found a gap between changeovers, because nobody had told him the crew was coming. One hour and fifty-five minutes into the shift, the crew had done no work on an asset. Later they stood in the compressor building for thirty minutes waiting for a changeover to finish.

At the end of the day: 31 labor hours paid. 11 hours and 20 minutes with hands on an asset. Wrench time: 36.5%.

Nobody on that crew was lazy. Every lost block had a cause in the system around them: a kit that was raided and never restocked, no window agreed with operations, a meeting with no agenda.

Wrench time benchmarks

Wrench time	Tier	What the shop looks like
Under 35%	Deep trouble	Parts are hunted, schedules collapse by Tuesday, the planner is firefighting.
35% to 55%	Recovering	PMs run, a schedule exists and holds some of the time. Most North American shops sit here.
55% to 65%	Decent: the target	The weekly schedule holds, kits are staged 48 hours ahead, break-in work is under 15%.
65% and above	World class	Condition monitoring on critical assets, reactive work under 10%, very few surprises.

The tiers follow Doc Palmer's Maintenance Planning and Scheduling Handbook, as used in Fix the System. The full one-pager below describes each tier, what it costs and what to do next.

How to measure wrench time in one day

Pick a normal day. Not a shutdown, not a big project day.
Tell the lead mechanic you will follow the crew, and why: you are timing the shop's support systems, not the people.
Log every change of activity for the whole shift on the Follow-a-Crew Field Audit Sheet. Mark only hands-on asset time as on the asset.
Do the math at the end: hands-on labor hours divided by paid labor hours.
Code the losses. Group the off-asset minutes by cause: parts, permits, waiting for operations, travel, meetings. The largest group is the first system to fix.

How to raise wrench time

Do not push the crew to work faster. Fix the system that eats the day, one at a time, starting with the largest loss from your audit. In most shops that is one of these:

Parts kitting: kits staged 48 hours ahead, so nobody walks the plant looking for a component.
Job plans: a maintenance job plan for every planned job, scoped on the floor.
A weekly schedule that holds: windows agreed with operations before the week starts. The schedule builder lays one out.
Short meetings: a morning huddle with a written agenda, under 15 minutes.

The Wrench-Time Self-Audit scores these systems so you can see which one to install first.

Questions planners ask

What is a good wrench time percentage?: 55% to 65% is a decent, well-run program in Palmer's tiers. 65% and above is world class. Under 35% means the shop is in deep trouble, and most North American shops sit somewhere between 35% and 55%.
How do you calculate wrench time?: Follow one crew for one normal shift and log every activity. Add up the labor hours spent with hands on an asset and divide by the labor hours paid. 11.3 hands-on hours out of 31 paid is 36.5%.
Does walking to the job count as wrench time?: No. Walking, travel, waiting, searching for parts, meetings and paperwork are all off the asset. Some walking is part of the job, but the audit will show how much, and a large share points to a parts or staging problem.
Will the crew resent being timed?: Less than you expect, if you say what you are measuring: where the day gets eaten, not whether anyone works hard enough. Share the results with the crew. They usually know the time-wasters better than anyone.

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The PDF remains the printable one-pager. This web guide is excluded from printing so it does not add pages to it.

Palmer's four tiers, and what your shop looks like at each one.

Wrench time is the fraction of a paid maintenance hour spent with hands physically on an asset doing maintenance work. Walking, waiting, searching, meeting, paperwork, and travel do not count.

Measured against a tier table first developed by Doc Palmer (Maintenance Planning and Scheduling Handbook) and refined across decades of Wireman's benchmarking work.

The four tiers

Tier 1 — Below 35%: Deep trouble

What the shop looks like:

Parts are hunted, not kitted. Technicians walk the plant looking for the right component.
Schedules collapse by Tuesday. The Monday meeting's schedule does not survive contact with the week.
Close-outs are three words. Repaired. RTO. The CMMS holds no learning.
The planner is firefighting. Real planning happens rarely, if at all.
Morning huddles run long, deliver little.
Break-in work overrides planned work multiple times per shift.

What it feels like from the inside: busy. Always busy. Never caught up.

The cost: Paying for roughly 2× the crew the plant is actually getting. Every additional hire is consumed by the existing inefficiency.

What to do next: Do not try to install ten systems at once. Pick the one biggest single source of loss (usually parts kitting) and install one system against it. Ninety days of discipline on one system moves the needle more than ninety days of memos.

Tier 2 — 35% to 55%: Recovering / North American average

What the shop looks like:

PMs run. Not all of them on time, but they run.
A scheduling process exists. It holds some of the time.
The planner does some real planning, but gets pulled into firefighting regularly.
Break-in work runs around 20-30% of the total.
Close-out quality is mixed — some useful data, much of it Repaired. RTO.

What it feels like from the inside: normal. This is where most North American maintenance shops actually sit. Managers at this tier often believe they are already at Tier 3.

The cost: Still paying for ~40% more capacity than the plant is extracting. A crew of twelve delivers the work of roughly seven to eight.

What to do next: Measure what is driving the gap. Usually three to five specific system failures are responsible for most of the loss. Install systems against those five. Target a 5-point gain per quarter. The path from 45% to 60% is a twelve-month project, not a memo.

Tier 3 — 55% to 65%: Decent / Target for a well-run program

What the shop looks like:

Weekly schedule holds. Compliance above 85%.
Kits are staged 48 hours ahead of planned work.
Planner is planning. 1:6 to 1:10 planner-to-technician ratio is intact.
Close-outs capture failure codes and meaningful notes.
Break-in work below 15%.
Morning huddles run in under 15 minutes with a written agenda.

What it feels like from the inside: calm. The shop is busy but not chaotic. People know what they are doing tomorrow. The manager spends most of their time coaching, not firefighting.

The upside: A crew of twelve delivers the work of roughly ten to eleven. Nearly two mechanic-equivalents recovered, without hiring. Budget defense becomes easy because the capacity is visible.

What to do next: Hold the line. Tier 3 is lost back to Tier 2 faster than it is reached. Audit the installed systems weekly. Coach the supervisors. Resist the pull toward "one more system" — the value is in the existing ones holding up.

Tier 4 — 65% and above: World-class

What the shop looks like:

Condition-based monitoring on critical assets.
Predictive maintenance informing the planning process.
Reactive work below 10%.
Close-out discipline produces a living reliability database.
Supervisors actively coach close-outs weekly.
The maintenance manager is publicly visible on the floor.

What it feels like from the inside: quiet. Very few surprises. When something fails, the response is already planned.

Who gets here: Fewer than 5% of North American plants, by Wireman's estimate. Mostly in petrochemical, aerospace, and pharmaceutical — industries where failure is either extremely expensive or extremely dangerous.

What to do next: Share what you've built with the industry. If you're here, other managers need to hear how you got from 55% to 65%+. The literature on crossing that last gap is thin.

How to measure yours

Use the companion Follow-a-Crew Field Audit Sheet (also at getov.xyz/toolkit/fix-the-system/ch01). One day, one crew, thirty minutes of math at the end.

Common objections to the benchmark

"Our work is different — those numbers don't apply to us." Plants in every industry have used these tiers for thirty years. Your work has specifics. The specifics do not change the math.

"Walking is part of the job." Some walking is. The percentage of time on walking that comes out of your field audit will still be a number. If it is 15%, that is information. If it is 35%, that is a system failure.

"My crew would resent being timed." You are not timing them. You are timing the shop's support systems. The distinction is real. When you explain it as "where is our day getting eaten" and not "are you working hard enough," most crews become allies within a week.

From Fix the System by Ivan Getov. Companion to Chapter 1: The Wednesday Crew That Did Nothing. getov.xyz/toolkit/fix-the-system/ch01/wrench-time-benchmarks. Free. No email required.

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