Insights · 1 November 2026 · 5 min read
Where did 115 minutes go? A 10-minute check for any factory
A simple daily calculation that shows how much production time your factory loses, and where it goes. With a real example from a Victorian manufacturer.
By Paul Niglia, Lean Six Sigma Master Black Belt
Most owners I meet know their factory could do more. Few know how much more, or where the time goes. Here is a check you can do this week with a calculator and one day’s production numbers.
The calculation
You need three numbers:
- Time available: paid production time in a day, after breaks.
- Time per unit: how long one unit takes at your slowest step.
- Units made: what actually came off the line that day.
The formula
Time used = units made × time per unit. Missing time = time available − time used.
A real example
At a Victorian door manufacturer we worked with, a three-person line had 440 minutes available (7.6 production hours), 17.1 minutes per door at the slowest step, and made 19 doors.
19 × 17.1 = 325 minutes used. 440 − 325 = 115 minutes unaccounted for.
That is 26% of the day, nearly two hours, gone every day. It is six or seven extra doors a day the line could have built with the same people and machines.
Where the time actually goes
Nobody was slacking. When we watched the line for three days, the missing time came from:
- Running out of things. Glue filler ran out, and steel frames weren’t ready when needed.
- Tools and machines. A staple gun failed, screwdriver bits didn’t suit the job, and the CNC faulted or waited on fixes.
- Rework. Doors needed filling and sanding after blunt CNC tooling caused blowouts.
- Searching and waiting. Operators hunted for the right frame or waited for a decision.
- No target. Without a clear number for the day, nobody could tell by 10 am that the day was slipping.
None of these show up in a cycle time study. They only show up when you reconcile the day.
What to do about it
- Do the calculation every day for two weeks. Write the missing minutes on a whiteboard on the floor.
- Ask the team to log every stoppage over 5 minutes, with the time and what happened. Paper is fine.
- Sort the log by total minutes lost. The top two or three causes are usually most of the problem.
- Fix causes, not symptoms. If materials run out, set a reorder point. If a tool fails, keep a spare and track its life.
- Set a target by time block, for example by morning tea, lunch and end of day, so problems surface early.
At this manufacturer, these fixes, plus a rebalanced line and dashboards the team runs themselves, took the business from manager-dependent to system-governed. Read the case study.