Free SLA Uptime Calculator

Calculate how much downtime your SLA allows. Enter any uptime percentage (like 99.9% or 99.99%) to see exact downtime periods per day, week, month, and year.

Popular SLA Levels

99% uptime
3.65 days/year downtime
99.9% uptime
8.77 hours/year downtime
99.99% uptime
52.6 min/year downtime
99.999% uptime
5.26 min/year downtime
99.95% uptime
4.38 hours/year downtime
99.5% uptime
1.83 days/year downtime

Frequently Asked Questions

What does 99.9% uptime mean?

99.9% uptime means your service can be down for up to 8 hours and 45 minutes per year, which breaks down to about 43 minutes and 50 seconds per month. This is a common SLA level for many web services.

How much downtime does 99.99% uptime allow?

99.99% uptime allows for 52 minutes and 35 seconds of downtime per year, or about 4 minutes and 23 seconds per month. This is considered "high availability" and requires robust infrastructure.

What's the difference between 99.9% and 99.99% uptime?

The difference is significant: 99.9% allows 8.76 hours of downtime per year, while 99.99% only allows 52.6 minutes per year - that's about 10 times less downtime. The cost and complexity of achieving 99.99% is much higher.

How is uptime percentage calculated?

Uptime percentage is calculated as:

(Total time - Downtime) / Total time × 100

For example, if a service is down for 1 hour in a month (730 hours, on average), the uptime would be: 
(730 - 1) / 730 × 100 = 99.86%

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OnlineOrNot is built for scale and runs millions of uptime checks every week. Thousands of software teams, including some of the world's leading brands have already made the switch from other uptime monitors.

Uptime Checks last week
11.5M
Users
3,825
Detected incidents last week
7,455

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      Adam H
      Maker of Noti

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      I tried @RozenMD's OnlineOrNot uptime monitoring, and for a few days got notifications of 2min down time.

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      Khaled Bentoumi
      Founder of Data to Page

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      Alex Bowles
      Founder of Casterlabs

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      Graham Lea
      Founder of Archium.io

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      It is easy to set up and very reliable. I have been using it for almost an year now.

      Rajat Saxena
      Founder of CourseLit

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      Thanks @RozenMD for making this awesome tool!

      Louis Barclay
      Founder of Cloakist

    • OnlineOrNot does the job for me.

      Charles Miller
      Software Architect at Atlassian
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