SLA Comparison
What Does Each Uptime SLA Mean?
See the real-world impact of each uptime level.
| SLA Level | Daily Downtime | Monthly Downtime | Yearly Downtime | Typical Use |
|---|---|---|---|---|
| 99% | 14m 24s | 7h 18m | 3d 15h 39m | Internal tools, staging |
| 99.5% | 7m 12s | 3h 39m | 1d 19h 49m | Content sites, blogs |
| 99.9% | 1m 26s | 43m 49s | 8h 45m 36s | Most SaaS products |
| 99.95% | 43s | 21m 54s | 4h 22m 48s | E-commerce, payments |
| 99.99% | 8.6s | 4m 23s | 52m 33s | Financial APIs, healthcare |
| 99.999% | 0.86s | 26s | 5m 15s | Infrastructure (AWS, Stripe) |
Understanding Uptime
What Does Your SLA Actually Mean?
What Is Uptime?
Uptime is the percentage of time your service is operational and accessible. A 99.9% uptime means your service can be down for up to 8 hours and 45 minutes per year.
Why It Matters
Every minute of downtime costs money. Gartner estimates the average cost at $5,600 per minute. Your SLA defines the maximum acceptable downtime for your customers.
How to Measure It
Real uptime is calculated from actual request data, not synthetic pings. Checking from more than one location and at short intervals gives you numbers you can trust.
Who Uses This
Who Needs an Uptime SLA?
SaaS Platforms
Most SaaS products target 99.9% uptime (8h 45m downtime/year). Enterprise customers often require 99.95% or higher in their contracts.
E-Commerce
Every second of checkout downtime is lost revenue. Payment APIs typically require 99.95% uptime to avoid cart abandonment.
Fintech & Payments
Financial APIs need 99.99% uptime (52 minutes/year max). Regulatory requirements often mandate strict availability guarantees.
Healthcare
Patient-facing APIs handling appointments, records, or telehealth need 99.99%+ uptime for compliance and patient safety.
FAQ
Frequently Asked Questions
What does 99.9% uptime mean?
99.9% uptime (often called 'three nines') means your service can be unavailable for a maximum of 8 hours, 45 minutes, and 36 seconds per year. That translates to about 43 minutes per month or 1.44 minutes per day.
How is uptime calculated?
Uptime is calculated as: (Total time - Downtime) / Total time × 100. For accurate measurement, use real request data from multiple monitoring regions rather than simple ping checks. Scheduled maintenance may or may not count against your SLA depending on the agreement.
What is the difference between 99.9% and 99.99% uptime?
The difference is 10x in allowed downtime. 99.9% allows 8 hours 45 minutes of downtime per year, while 99.99% allows only 52 minutes 35 seconds. Achieving 99.99% requires redundant infrastructure, automated failover, and multi-region deployment.
What happens when an SLA is breached?
When an SLA is breached, the service provider typically owes service credits to the customer, usually 10-30% of the monthly bill per percentage point below the guaranteed uptime. Repeated breaches can trigger contract termination clauses.
Free Uptime Calculator for DevOps Teams
This free uptime calculator helps DevOps teams, SREs, and engineering managers convert SLA uptime percentages into real downtime numbers. Whether you're negotiating an SLA with a vendor, defining your own service level objectives (SLOs), or explaining to stakeholders what '99.9% uptime' actually means, this tool gives you the exact numbers.
Understanding the real cost of each 'nine' in your uptime target is critical for infrastructure planning. The jump from 99.9% to 99.99% doesn't sound like much, but it means reducing your allowed yearly downtime from 8 hours to just 52 minutes, requiring fundamentally different architecture decisions.