An SLA (Service Level Agreement) is a contractual commitment between a service provider and a customer that defines a minimum level of availability. This SLA uptime calculator translates any availability percentage into concrete downtime, or works in reverse to check whether a real outage breached your SLA.
How availability is calculated
Availability is expressed as a percentage of total time the service was operational:
Availability % = (Total Time − Downtime) / Total Time × 100
SLAs are often expressed as how many nines they contain in the percentage. 99.9% vs 99.99% is the difference between 43 minutes of downtime per month and 4.4 minutes. Do the math on the cost of every minute of downtime for your business and you will have a good idea of how many nines you need — though the right level varies by industry, user expectations, and what your infrastructure can realistically sustain.
For a full breakdown, see our uptime monitoring guide.
What counts as downtime
Your SLA should specify what is actually included in the calculation of the real availability – the number that holds the provider accountable.
Some periods of downtime may not count toward the calculated availability, such as scheduled maintenance windows, partial outages, incidents below a minimum duration threshold, and failures caused by third-party services or the customer.
Read the exclusions and then measure your own downtime by the same rules.
Verifying your SLA
Use this calculator to evaluate a provider's commitment before signing, or to check whether an outage breached your SLA. For independent verification, Testomato's uptime monitoring and response time monitoring give you your own data — useful when reviewing your provider's reports or building evidence for a credit claim.