FAQ

How long is a month?

An average month of 30.44 days. Quarters are 90 days and years are 365 days.

Why does 5 mean 99.999% and not 5%?

Any value from 1 up to (but not including) 16 is read as a number of nines, so 1 is 90%, 3 is 99.9% and 3.5 is 99.968%. Service levels that low aren't realistic targets, so the shorthand takes priority. If you do mean a plain percentage, add the percent sign: 5% is 5%.

What does hours per day change?

It shortens every period. With 12 hours, a week is 7 × 12 hours, which suits a service that only has to be up during business hours. It applies to reverse calculations too.

Why is a period marked as not achievable?

The repair time for your expected incidents (MTTR × incidents) already uses up the whole downtime budget for that period, so there's no time left to detect them. Lower the MTTR or the incident count, or pick a longer period.

How do I write the mean time to repair?

Days, hours, minutes and seconds in that order, each optional: 1d, 90m, 1h30m, 2d4h.

Can I share a calculation?

Yes. The page address updates as you type, so copying it shares the same inputs.