Uptime & Downtime Calculator - Calculate Service Availability
Calculate actual downtime from uptime percentage or determine required uptime from allowed downtime. Get detailed breakdowns across multiple time periods. Monitor your server with Port Scanner or check reliability with SSL Checker.
Key Features
- Bidirectional calculation (uptime ↔ downtime)
- Multiple time periods (daily to yearly)
- Detailed downtime breakdowns
- Reliability tier classification
- Industry standard comparisons
Use Cases
- SLA planning and monitoring
- Infrastructure reliability assessment
- Service level agreement validation
- Uptime requirement planning
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Login with GoogleCalculate actual downtime from uptime percentage or determine required uptime from allowed downtime. Get detailed breakdowns across multiple time periods.
Or choose a general preset:
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What does 99.9% uptime mean?
99.9% uptime (also called "three nines") means your service is available 99.9% of the time, allowing for approximately 43.2 minutes of downtime per month or 8.76 hours per year. This is a common SLA target for many web services.
How is uptime calculated?
Uptime is calculated as: (Total Time - Downtime) / Total Time × 100. For example, if a service is down for 30 minutes in a 30-day month (43,200 minutes), the uptime is (43,200 - 30) / 43,200 × 100 = 99.93%.
What's the difference between 99.9% and 99.99% uptime?
While seemingly small, the difference is significant. 99.9% allows ~43.2 minutes of downtime per month, while 99.99% ("four nines") allows only ~4.3 minutes per month. Enterprise-grade services often target 99.99% or higher. Use our SSL Checker to ensure your certificates won't cause unexpected downtime.
How can I monitor my server's uptime?
Monitor uptime using tools like Port Scanner to verify services are running, DNS Lookup to check domain health, and external monitoring services that ping your server at regular intervals and alert you to downtime.
This calculator helps you understand the real-world impact of uptime percentages by converting them to actual downtime durations. It supports bidirectional calculation: determine downtime from uptime percentage, or calculate the required uptime for a given downtime allowance. Perfect for SLA planning, infrastructure monitoring, and understanding service reliability commitments.