Uptime
How much downtime is 99.9% uptime?
99.9% uptime allows 8 hours 45 minutes 36 seconds of downtime a year and 43 minutes 48 seconds a month. See what three nines means for your site.
Updated 5 min read
99.9% uptime, three nines, is the usual promise for professional websites and the most common figure in hosting agreements. It allows about 44 minutes of downtime a month.
| Period | Allowed downtime at 99.9% |
|---|---|
| Per day | 1 min 26 s |
| Per week | 10 min 5 s |
| Per month | 43 min 48 s |
| Per year | 8 h 45 min 36 s |
What does 99.9% uptime mean in practice?
Three nines is where outages stop being something you can afford to find out about later. A single bad deploy or an expired certificate can use the whole month's allowance in one go, so the target is only realistic with monitoring and a quick response.
Who is 99.9% uptime right for?
- Client business sites and shops
- Marketing sites that drive revenue
- Small SaaS products in their first years
Who should aim higher?
Payment systems and anything with a contractual penalty for downtime. Those usually need four nines and redundancy.
What does it take to reach 99.9% uptime?
Three nines normally needs reliable hosting, external checks every one to five minutes with confirmed alerts, automatic certificate renewal that you watch, and a way to roll back a bad release quickly.
How is the downtime calculated?
The allowed downtime is the length of the period multiplied by the share of it you may be down: period x (100 - 99.9) / 100. The table uses a month of one twelfth of a 365-day year. A contract that says "per month" may define a month differently, so check the wording. Use the uptime and SLA calculator for any other percentage, or to turn the downtime you had into an uptime figure.
How do I know what uptime I actually deliver?
You cannot promise an uptime you do not measure. Run external checks that confirm failures before alerting, keep the check history and report the real number each month. Our guide on setting up uptime monitoring for client websites shows how.
Where Datumboard fits
Datumboard shows the health of every client site next to deploys, renewals, search data and costs, so a failing site is at the top of one list. It is in early access, and you can join the list below.
Frequently asked questions
How much downtime is 99.9% uptime?
43 minutes and 48 seconds per month, 10 minutes and 5 seconds per week and 8 hours 45 minutes 36 seconds per year, using a month of a twelfth of a 365-day year.
Is 99.9% uptime good?
Yes. It is the standard target for professional websites and is achievable on good hosting with monitoring.
Can an expired certificate break a 99.9% target?
Easily. One expired certificate that goes unnoticed for an hour uses more than a whole month's allowance of 43 minutes on its own.
Keep reading
- UptimeHow much downtime is 99.5% uptime?99.5% uptime allows 1 day 19 hours 48 minutes of downtime a year, or 3 hours 39 minutes a month. Learn what it means and when it is enough.Read
- UptimeHow much downtime is 99.95% uptime?99.95% uptime allows 4 hours 22 minutes 48 seconds of downtime a year and 21 minutes 54 seconds a month. Learn who needs it and what it takes.Read
- How-toSSL certificate expired? How to fix itVisitors see a full-page browser warning. Confirm the certificate expired, renew it for your kind of hosting, verify the fix and stop it happening again.Read
- Free toolUptime and SLA calculator (free)Turn an uptime percentage into the downtime it allows per day, week, month and year, or work out the uptime you actually had from minutes of downtime.Read