Uptime SLA calculator
“We guarantee 99.9%” sounds precise until someone asks what it actually permits. It is about 44 minutes a month — which is a long time for a checkout page.
How much downtime does my SLA allow?
Per day1m 26s
Per week10m 5s
Per month43m 50s
Per quarter2h 11m
Per year8h 45m
Months are the average Gregorian month, not a flat 30 days — the difference is a couple of seconds, and the accurate one is what belongs in a contract.
What uptime did an outage cost me?
99.861%below a 99.9% promise
Knowing the number is not the hard part
The difficulty is noticing you are spending the allowance. An outage at 2am that nobody sees until morning has already used six hours of a 99.9% year. AlertKite watches the site and tells you on WhatsApp, Slack or email the moment a failure is confirmed — and gives you a monthly page showing the uptime you actually delivered, which is the thing your client wanted the percentage for.