SLA Uptime Calculator
Calculate how much downtime your SLA actually allows. Understand what 99.9%, 99.99%, or 99.999% availability really means for your service.
Calculate Your Allowed Downtime
SLA Uptime Percentage
%
Common SLA Levels
| SLA | Per Day | Per Week | Per Month | Per Year |
|---|---|---|---|---|
| 99% | 14m 24s | 1h 40m | 7h 18m | 3d 15h |
| 99.9% | 1m 26s | 10m 4s | 43m 49s | 8h 45m |
| 99.95% | 43s | 5m 2s | 21m 54s | 4h 22m |
| 99.99% | 8.6s | 1m | 4m 23s | 52m 33s |
| 99.999% | 0.86s | 6s | 26s | 5m 15s |
Downtime Breakdown
- Per Day: 1m 26s
- Per Week: 10m 4s
- Per Month: 43m 11s
- Per Year: 8h 45m
How It's Calculated
Downtime = Total Time × (100% - Uptime%)
What is Uptime?
Uptime is the percentage of time a system, service, or website is operational and accessible. It's a key metric for measuring reliability and is typically expressed as a percentage of the total time in a given period.
Understanding SLA Levels
Service Level Agreements (SLAs) define the expected uptime for a service. The "nines" terminology refers to the number of 9s in the uptime percentage:
- 99% (Two Nines) - Allows about 3.65 days of downtime per year
- 99.9% (Three Nines) - Allows about 8.76 hours of downtime per year
- 99.99% (Four Nines) - Allows about 52.56 minutes of downtime per year
- 99.999% (Five Nines) - Allows about 5.26 minutes of downtime per year
Why Uptime Matters
Every minute of downtime can impact your business through lost revenue, damaged reputation, and decreased customer trust. Understanding your SLA helps you set realistic expectations with customers and plan your infrastructure accordingly.
Frequently Asked Questions
How is uptime percentage calculated?
Uptime percentage is calculated as: (Total Time - Downtime) / Total Time × 100. For example, if your service was down for 1 hour in a month (730 hours), your uptime would be (730-1)/730 × 100 = 99.86%.
What is a good uptime percentage?
For most business-critical applications, 99.9% (three nines) is considered a good baseline. Mission-critical systems often aim for 99.99% or higher. The right target depends on your business needs and the cost of downtime.
Does scheduled maintenance count as downtime?
This depends on how your SLA is defined. Some SLAs exclude scheduled maintenance windows, while others include all unavailability. Always check the specific terms of your SLA.
How do cloud providers measure uptime?
Major cloud providers like AWS, Azure, and Google Cloud typically offer SLAs of 99.9% to 99.99%. They usually measure uptime per service and per region, with service credits offered when targets are missed.
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