Website Uptime Calculator
Convert a website or service's uptime percentage into the equivalent downtime in minutes per day, month and year.
Your results
Calculation breakdown
- Downtime fraction
- (100 − uptime%) ÷ 100
- Minutes per year
- 365 × 24 × 60 × downtime fraction
Worked example
A 99.9% uptime target allows about 8 hours 46 minutes of downtime per year, or roughly 43 minutes per month.
Assumptions
- Assumes downtime is measured continuously over the full calendar period.
- Actual SLA terms may exclude scheduled maintenance from downtime counts — check the provider's SLA.
How this calculator works
Enter an uptime percentage such as 99.9% to see the equivalent allowed downtime per day, month and year — the classic 'nines of availability' table used when comparing hosting or SLA commitments.
Frequently asked questions
What does 99.9% uptime mean in practice?
99.9% uptime allows about 8 hours 45 minutes of downtime per year, or roughly 43 minutes per month.
What is considered 'high availability'?
99.99% ('four nines') or better is often considered high availability, allowing only about 52 minutes of downtime per year.
Is 100% uptime realistic?
No, virtually no real-world system guarantees 100% uptime; even major cloud providers publish SLAs below that figure.