What does website downtime really cost us per year?
Most teams quote a single number for downtime: revenue per hour. That number quietly ignores the engineering scramble, the make-good credits, and the customers who never come back. This model simulates a full year of outages and hands you an expected bill, a bad year number, and the honest price of one more hour down.
Operations Intermediate Monte Carlo Pro engine
After you install, this is the model to open.
What Does an Hour of Website Downtime Cost?
- In your spreadsheet, click the Sortia icon in the strip of icons down the right-hand edge. No strip? Click the arrow at the bottom-right to open it. You can also use Extensions, then Sortia, then Open Sortia.
- Click Start from a template and put that name in the search box.
- Pick the card with that name and click Load this template. It arrives on a new tab with real numbers already in it.
This one runs on a Pro engine, and every free install includes five full-quality runs on your own numbers, shared across all five Pro engines rather than five for each. After that, Pro is $199/year.
The answer
One click returns the full distribution of this year's downtime bill, plus the marginal cost of a single extra hour.
- Expected cost this year
- $69,000 average of 10,000 simulated years
- Bad year (P90)
- $131,000 one year in ten costs at least this
- True cost of one more hour
- $4,800 2.4x the $2,000 revenue-per-hour figure
- Share that is not lost sales
- 79% crisis response plus lost customers
At these assumptions an average year costs $69,000, but one year in ten runs to $131,000 or worse, and one year in five clears $100,000. Only 21% of that total is the lost sales everybody counts; the other four fifths is crisis response and customers who never return. The number worth arguing about is the last one: an extra hour of downtime really costs about $4,800, so redundancy work that removes six hours a year is worth roughly $29,000 before it has saved a single sale.
The model
The sheet holds seven assumptions about how often your site fails and what each failure costs. Five of them are ranges rather than single numbers, so Sortia plays the year out 10,000 times.
| Annual online revenue | $17,520,000 (that is $2,000 per hour) |
| Unplanned outages this year | 0 to 10, averaging 4 (uncertain) |
| Average outage length | 0.5 h – 1.8 h – 8 h (uncertain) |
| Share of lost orders recovered later | 10% – 30% – 55% (uncertain) |
| Crisis response cost per outage | $1,000 – $3,000 – $10,000 (uncertain) |
| Future revenue lost to churn, per hour down | $800 – $2,500 – $7,000 (uncertain) |
| Cost of one more hour down | calculated from the above |
Once it is in your sheet
- The model arrives with real numbers in it and runs as it stands, so you can press the button first and understand it second.
- Change the numbers to yours. The sheet marks which cells are inputs and which hold formulas, and most labels carry a note explaining the row.
- Press the run button at the bottom of the panel. It is labeled for the tool you are in, and the result lands on its own tab, with a written reading of it beside the figures.
Never used Google Sheets? Start here goes the whole way, in seven steps, and assumes nothing.
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Every model like this one, and the method behind them: Monte Carlo simulation.