Downtime Cost Calculator
The full cost of an hour of downtime — lost output, idle labour, restart scrap and any penalties — and what that makes a reliability investment worth.
Lost output is the obvious cost, and it is usually not the largest.
How the downtime cost calculator works
Lost output is the obvious cost, and it is usually not the largest. Labour is still paid while the line is down; restarting scraps material and takes time; and a late delivery may carry a penalty. Added together, an hour of downtime on a line producing 2,000 of margin an hour routinely costs 4,000.
That number is what makes a maintenance contract, a spare part on the shelf or a redundant machine easy to justify — and why it is worth computing rather than guessing.
Formula: cost per hour = lost margin + idle labour + restart scrap / restart hours + penalties
Worked examples
| Inputs | Cost per hour of downtime | Note |
|---|---|---|
| A line at 320 units an hour | 2,632 | about 2,600 an hour |
| With a penalty | 4,132 | much higher |
| Fewer, longer events | 2,362 | the same hours, lower restart share |
FAQFrequently asked questions
What does downtime cost?
Far more than the lost output. Idle labour, restart scrap, expediting and penalties often double it — which is why plants that only count output under-invest in reliability.
Why include idle labour?
Because it is paid whether the line runs or not. If people cannot be redeployed to useful work during a stoppage, their cost is a downtime cost.
What is restart cost?
Scrap made while the process settles, plus the time to bring it back to rate. It is a per-event cost, so many short stoppages cost more than one long one.
How do I use the investment figure?
As the ceiling for a reliability spend. A spare on the shelf, a maintenance contract or a redundant unit that halves downtime is worth up to that amount.
Does availability matter more than the cost?
They are the same fact. Ninety-nine per cent availability is 88 hours a year of downtime; at 2,600 an hour that is 228,000.
Where these figures come from
- Nakajima (1988) — Introduction to TPM — the origin of Overall Equipment Effectiveness and its six big losses
- Health and Safety Executive — the UK workplace safety regulator
Last checked: September 2026. Definitions follow standard operations-management practice; where plants commonly differ, the page says so.