Cost of Downtime Calculator

Put a dollar figure on lost production and standby labour

Inputs

Downtime per event (hours)Events per year Lost throughput (units / hour)Production you would have made while the asset was down.Contribution margin ($ / unit)Margin lost per unit not produced, not full sale price.Standby labour (people)Labour rate ($ / hour)

Lost production per event

$16,000

Standby labour per event

$2,880

Cost per event

$18,880

Annual cost of downtime

$226,560

12 events × $18,880 per event

How it's calculated

Lost production

Downtime × throughput × margin

Standby labour

Downtime × people × rate

Cost per event

Lost production + labour

Annual cost

Cost per event × events / year

Lost production per event = downtime hours × lost throughput × contribution margin.

Standby labour per event = downtime hours × people standing by × labour rate.

Cost per event = lost production + standby labour.

Annual cost = cost per event × events per year.

Use contribution margin rather than full sale price so the figure reflects profit actually forgone. It is a directional estimate, not a substitute for detailed loss accounting.

How to calculate the cost of downtime: a worked example

Take a conveyor that stops the plant for four hours at a time, 12 times a year, using the figures the calculator opens with. While it is down the plant loses 500 tonnes an hour at a contribution margin of $8 a tonne, and six people stand by at $120 an hour.

Step	Calculation	Result
Lost production per event	4 h × 500 t/h × $8/t	$16,000
Standby labour per event	4 h × 6 people × $120/h	$2,880
Cost per event	$16,000 + $2,880	$18,880
Annual cost	$18,880 × 12 events	$226,560
Cost per hour of downtime	$18,880 ÷ 4 h	$4,720

At $4,720 an hour, a fix that saves two hours per event is worth more than $110,000 a year before anything else changes.

The cost of downtime formula

Cost per event = (downtime hours × lost throughput × contribution margin) + (downtime hours × people standing by × labour rate). Multiply by events per year for the annual figure, or divide by downtime hours for a cost per hour, the number most business cases lead with.

Use contribution margin, the sale price less the variable cost of producing a unit, rather than revenue. Variable costs such as energy and consumables are not spent while the plant is stopped, so revenue overstates the loss.

The formula covers the two costs almost every stoppage carries. Depending on the event, add repair labour and parts, contractor call-outs, penalties or demurrage, and restart losses such as off-spec product. Safety and environmental consequences matter more than any of these and rarely belong in a single cost figure.

When lost production is really lost

Downtime only costs production on the constraint. An hour lost on equipment with spare capacity downstream can often be made up. An hour lost on the bottleneck is gone.
Check whether the plan had slack. If the plant was scheduled below capacity, some output can be recovered in the next shift, and the true cost is lower than the formula suggests.
Buffers delay the loss rather than prevent it. A stockpile or surge bin can carry a downstream plant through a short stop, but a long one will run it empty.
Count every event, not just the memorable ones. Fifty one-hour stops cost about as much as 12 four-hour ones, and the short stops rarely make the monthly report.

Why it matters

Downtime gets talked about in hours, but decisions get made in dollars. Put a defensible number on a stoppage, the production margin you lose plus the crew standing around, and reliability spend stops looking like a cost and starts looking like an investment against a loss you can measure. That number is usually what gets a business case over the line.

The annual view is where it bites. A four-hour stop that feels routine can quietly cost more over a year than a headline capital project, once you count how often it happens. Costing it this way helps you decide which failures to engineer out first, shows what faster response and better spares are worth, and gives operations and finance the same language for the cost of things breaking.

Common questions

How do you calculate the cost of downtime?

Multiply downtime hours by the lost throughput and the contribution margin per unit, then add the cost of people standing by, which is downtime hours multiplied by headcount and labour rate. Multiply the cost per event by the number of events per year for an annual figure.

What is the average cost of downtime per hour?

It varies too widely for an average to mean much. It depends on throughput, margins and whether the stopped equipment is the bottleneck. A figure calculated from your own throughput and margin is far more useful than an industry number.

Should the cost of downtime use revenue or margin?

Margin. Contribution margin, the sale price less variable production cost, reflects the profit actually lost, because variable costs such as energy and consumables are not spent while the plant is stopped. Revenue overstates the loss.

Is all downtime equally expensive?

No. Downtime on the constraint loses output that cannot be recovered, while downtime on equipment with spare capacity or buffer storage may cost little beyond labour. Identify the bottleneck before putting a price on an hour.

How do you reduce the cost of downtime?

Make failures less frequent, make recovery faster, or protect the constraint. An asset criticality assessment shows where to focus, reliability work reduces how often failures happen, and planning, spares and access reduce how long each one lasts.

Want to improve the numbers?

These calculators reflect the work we do every day. If you want help lifting availability, cutting downtime or tightening your schedule, let's talk.