Calculate allowed downtime for SLA percentages like 99.9%.
Results
What is Uptime Calculator?
Uptime Calculator converts SLA uptime percentages into actual allowed downtime per year, month, week, and day. Enter a percentage like 99.95% and instantly see that it means 4.4 hours of downtime per year. Includes an SLA comparison table.
How to use this tool
Enter an uptime percentage (e.g., 99.95).
See allowed downtime calculated for year, month, week, and day.
Check the SLA class (Basic, Standard, Business, Enterprise).
Compare with the reference table showing common SLA tiers.
Use the results for SLA negotiations or infrastructure planning.
Frequently asked questions
What does "five nines" mean?
99.999% uptime — only 5.26 minutes of downtime per year. It's the gold standard for critical infrastructure. Each additional nine dramatically reduces allowed downtime: 99.9% allows 8.7 hours, 99.99% allows 52 minutes.
What SLA should I aim for?
99.9% (three nines) is standard for most web applications — about 8.7 hours/year downtime. 99.95% or higher for e-commerce and SaaS. Four and five nines require redundant infrastructure and are expensive.
Does planned maintenance count as downtime?
Depends on the SLA contract. Many providers exclude scheduled maintenance windows from their uptime calculation. Read the fine print — some define "downtime" as only unplanned outages lasting more than 5 minutes.
How is uptime actually measured?
External monitoring services (Pingdom, UptimeRobot) check your site every 1-5 minutes from multiple locations. Downtime is counted when the site fails to respond or returns errors. Most providers have their own internal monitoring for SLA compliance.