Reliability · Business impact
Downtime cost calculator.
Enter what an hour of downtime costs you and an availability level to see the yearly exposure. The cost per hour is your figure; none is assumed.
Inputs
Result
Enter the values above.
How to estimate the cost of downtime
Cost of downtime = hours of downtime x your cost per hour. The hours come from the availability target: (1 - availability) x hours in the period, so 99.9% over a 365-day year (8,760 hours) allows 8.76 hours (Google SRE Book availability table). At 5,000 per hour that is 43,800 a year of exposure if you use the whole allowance.
This tool deliberately includes no industry cost-per-hour averages, because published figures vary widely by company and method. Build your own number from lost revenue, staff time, SLA credits you pay out, and recovery cost. Compare the yearly exposure at 99.9% and 99.99% with what the extra nine would cost to engineer.
Frequently asked questions
How do I calculate the cost of downtime?
Multiply hours of downtime by your cost per hour. Include lost revenue, staff time and any SLA credits.
What is the average cost of downtime per hour?
There is no single reliable figure; it depends heavily on the business. This tool uses only the number you enter.
Is the result what I will actually lose?
No. It is the exposure if you use the full allowed downtime. Actual downtime is usually lower, and some outages cost more than the average hour.
Is the extra nine worth it?
Compare the yearly exposure saved with the engineering and operating cost of the higher target.
Sources
Checked
- Google SRE Book: Appendix A, Availability Table
- AWS Well-Architected Reliability Pillar: Availability
Formulas follow the sources above. Periods use a 30-day month and a 365-day year. Runs entirely in your browser; nothing you type is sent or stored.
Scope
Planning estimates only. Your SLA contract defines its own measurement window, exclusions and remedies, and those override these generic figures. Theoretical availability assumes independent failures.