// Key takeaway
99.9% uptime allows about 8.8 hours of downtime a year, 99.95% about 4.4 hours and 99.99% about 53 minutes. Check how it's measured and what's excluded.
The numbers
99.9% allows around 8 hours 46 minutes of downtime a year. 99.95% allows around 4 hours 23 minutes. 99.99% allows around 53 minutes.
How it's measured
Ask whether uptime is measured monthly or annually, from where, and whether partial outages count.
What's excluded
Planned maintenance, customer-caused issues and third-party failures are commonly excluded. Know the exclusions before relying on the headline figure.
What really matters
An SLA is a promise with compensation attached, but compensation rarely covers lost business. Architecture, monitoring and a responsive team matter more than the percentage.
Published 16 October 2026 by the Digital Hosting Services engineering team, York.
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