SLA and Uptime Calculator

Turn an uptime percentage into the downtime it allows per day, week, month, quarter and year.
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What is uptime?

Uptime is the amount of time that a service is available and operational, typically expressed in percentage.

What is SLA?

A service-level agreement (SLA) defines the level of service you expect from a vendor, laying out the metrics by which service is measured, as well as remedies or penalties should agreed-on service levels not be achieved.

How to prevent downtime?

Redundancy, monitoring and alerting are key to ensure a safe and reliable service. Odown is here to help with monitoring your critical infrastructure.

What is the uptime percentage?
%
Daily1d
Weekly7d
Monthly30d
Quarterly91.25d
Yearly1y

When you signup with a service vendor, you need to understand what uptime promises they guarantee and what those percentages mean. For context, an SLA of either 95 or 98 percent availability per year sounds amazing, but do you know what that really means to your business or online service? At 95%, you can expect around 18 days of unexpected downtime. At 98%, you can expect over 7 days a year of downtime. You will need to evaluate your critical business needs and say to yourself can you afford this sort of downtime?

Common uptime percentages and the downtime they allow

Each extra nine cuts the allowed downtime by ten. Figures use a 30-day month and a 365-day year.

UptimeAlso calledPer dayPer monthPer year
99%Two nines14 minutes 24 seconds7 hours 12 minutes3 days 15 hours 36 minutes
99.5%7 minutes 12 seconds3 hours 36 minutes1 day 19 hours 48 minutes
99.9%Three nines1 minute 26 seconds43 minutes 12 seconds8 hours 45 minutes 36 seconds
99.95%43 seconds21 minutes 36 seconds4 hours 22 minutes 48 seconds
99.99%Four nines9 seconds4 minutes 19 seconds52 minutes 34 seconds
99.999%Five nines1 second26 seconds5 minutes 15 seconds

SLA and uptime FAQ

What does five nines availability mean?

Five nines is 99.999% uptime. It allows about 5 minutes 15 seconds of downtime a year, or 26 seconds a month. It usually needs redundant systems in several locations and automatic failover, so it's mostly promised for critical infrastructure.

How is allowed downtime calculated?

Allowed downtime = (100% − uptime %) × the length of the period. For example, 99.9% over a 30-day month is 0.1% × 43,200 minutes = 43.2 minutes. This calculator uses a 30-day month, a 91.25-day quarter and a 365-day year.

How do I turn downtime into an uptime percentage?

Uptime % = (total time − downtime) ÷ total time × 100. For example, 2 hours of downtime in a 30-day month (720 hours) is (720 − 2) ÷ 720 × 100 = 99.72%.

Is 99.9% uptime good?

For most websites and SaaS products, 99.9% is a common SLA target. It allows about 43 minutes of downtime a month. Lower targets such as 99.5% allow several hours a month, which customers usually notice.

How do I know if a vendor is meeting its SLA?

Measure it yourself rather than relying on the vendor's own status page. An external uptime monitor that checks the service every minute records every outage and how long it lasted, so you can compare real uptime with what the SLA promises.

Read more: is 99.5% uptime good enough?, does scheduled maintenance count against SLA uptime? and the difference between SLAs, SLOs and SLIs. To check whether a site is up right now, use the free website uptime checker.

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