Uptime Calculator
Calculate allowed downtime for any SLA uptime percentage. See downtime per day, week, month, and year.
SLA Nines Reference
Standard SLA tiers and their allowed downtime budgets
| Uptime % | Nines | Downtime/Year | Downtime/Month | Downtime/Day |
|---|---|---|---|---|
| 99% | Two Nines | 3.65 days | 7.31 hours | 14.40 min |
| 99.9% | Three Nines | 8.77 hours | 43.83 min | 1.44 min |
| 99.95% | Three and a Half | 4.38 hours | 21.92 min | 43.20 sec |
| 99.99% | Four Nines | 52.60 min | 4.38 min | 8.64 sec |
| 99.999% | Five Nines | 5.26 min | 26.30 sec | 0.86 sec |
Understanding Uptime & Availability
Learn the key concepts of service reliability, SLAs, and how to maintain high availability for your applications.
What is an SLA?
A Service Level Agreement (SLA) is a contract between a service provider and a customer that defines the level of service expected. It typically includes uptime guarantees, response times, and penalties for not meeting these standards.
The Cost of Downtime
Downtime can be expensive. For e-commerce sites, it means lost sales. For SaaS, it means lost productivity and potential SLA penalties. Gartner estimates the average cost of IT downtime is $5,600 per minute.
High Availability (HA)
High Availability refers to systems designed to operate continuously without failure for a long time. HA systems use redundancy, failover, and load balancing to ensure services remain accessible even if components fail.
Monitoring Best Practices
To ensure high uptime, implement comprehensive monitoring. Check from multiple locations, monitor different protocols (HTTP, TCP, ICMP), and set up alerts to respond immediately to incidents before they affect users.
Planned vs Unplanned
Distinguish between planned maintenance and unplanned outages. Many SLAs exclude planned maintenance windows from uptime calculations, provided they are communicated in advance.
Reliability Engineering
Site Reliability Engineering (SRE) applies software engineering principles to infrastructure and operations. SREs focus on creating scalable and highly reliable software systems.
Frequently Asked Questions
What do the nines mean in uptime? expand_more
What uptime percentage should my SLA target? expand_more
Does uptime include planned maintenance? expand_more
How is uptime measured? expand_more
What is the difference between availability and uptime? expand_more
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