How much downtime is 99% uptime?

99% uptime, often called two nines, sounds high and is not. It allows more than three and a half days of downtime a year, which is enough for a long weekend outage nobody notices until Monday.

What does 99% uptime mean in practice?

Two nines is the level you get by default from a single cheap host with no monitoring and no one watching. It tolerates a site being down for most of a working day once a month, so it only suits something nobody depends on.

Who is 99% uptime right for?

• A personal project or hobby site
• An internal tool used a few times a week
• A staging or demo environment

Who should aim higher?

Anything a client pays for. A client site that is down for seven hours in a month is the kind of problem that produces an uncomfortable phone call, and 99% would call that on target.

What does it take to reach 99% uptime?

Reaching 99% needs little more than a working host and an alert when it fails. The risk is not the percentage, it is that nobody finds out about the outage until a visitor does.

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) / 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.