Downtime Cost Calculator

Why The Usual Number Is Too Low

Ask a plant what an hour of downtime costs and you will usually get one calculation: units not made, multiplied by price. That understates it in three ways.

Labour keeps running. A stopped line rarely means a stopped crew. Six people at a fully loaded rate is real money leaving the building whether or not anything is being produced.

Restarts are not free. Most processes produce out-of-spec product for a period after a restart — coming back up to temperature, pressure, or registration. That scrap belongs to the downtime event that caused it.

Recovery costs land later. Overtime to catch up, expedited freight to protect a delivery date, and the callout you paid for at 2am all trace back to the same stoppage, but they usually get booked somewhere else entirely.

Add those and the real number is commonly two to three times the headline figure — which is exactly why maintenance budgets are hard to justify using the headline figure.

What To Do With The Number

• Rank your assets by it. The same hour of downtime costs wildly different amounts depending on where it happens. Your PM effort should follow that curve, not asset count.
• Use it to price a PM. If a quarterly oil sample costs 1.5 hours and buys off a failure that would take the line down for two days, the arithmetic stops being an argument.
• Take it to the budget conversation. "We need a CMMS" loses. "Unplanned downtime costs us this much a year and here is the 20% we can take out of it" wins.

Then run the CMMS ROI calculator to turn it into a full business case, or the PM interval calculator to find the interval where prevention actually pays.