Wrench time is the time a technician spends performing hands-on work at the job site, from starting the work to finishing it. It excludes driving, waiting, paperwork away from the job and shop time.
How to calculate wrench time
With job-level timestamps, wrench time per job is:
Wrench time = Work complete − Work started (or arrived, if start is not captured)
Summed across a period and divided by available hours, it becomes a percentage:
Wrench time % = Total wrench time ÷ Available hours × 100
Say a technician works a 9-hour paid day. They drive for 2.5 hours, wait on access or parts for 1 hour, spend 0.5 hours on lunch and 0.5 on paperwork at the shop. That leaves 4.5 hours of wrench time, or 50% of the day. The technician utilization calculator splits a day the same way.
Why it matters for scheduling
Wrench time is the honest numerator for technician utilization rate. It answers whether the schedule is putting technicians in front of work, not just whether the calendar is full.
Scheduling moves it from both sides. Less driving between jobs gives more hours for work. Accurate job duration estimates mean fewer half-finished visits and fewer gaps where a technician arrives before the next job is ready. The relationship between booked hours and real work hours is covered in Technician utilization rate: the formula.
A common mistake
Using arrival-to-departure as wrench time. That span includes finding the customer, waiting for access, staging tools and talking through the invoice. It is closer to "on-site time." If you only have arrival and departure, call the number on-site time and accept that it runs higher than true wrench time.
The opposite mistake is treating low wrench time as a technician problem. If a technician spends three hours a day driving, their wrench time is set by the schedule they were handed.
Related terms
- Windshield time is the driving half of the day.
- Idle time is paid time that is neither work nor travel.
- Technician utilization rate uses wrench time as its productive numerator.
Common questions
Where does the term wrench time come from?
It comes from maintenance and industrial work, meaning time with a tool in hand. In field service it has come to mean any hands-on work at the customer site.
Is on-site time the same as wrench time?
Not quite. On-site time runs from arrival to departure and includes setup, waiting and conversation. Wrench time is the working portion inside it.
How do I start measuring wrench time?
Capture four timestamps per job: dispatched, arrived, work complete and departed. Most field apps record these. The reporting often throws them away.