Interpreting Uptime Percentages
Uptime percentage is one of the most important metrics for your websites.
How It's Calculated
Uptime is calculated as:
Uptime % = (Successful checks / Total checks) x 100
For example, if your site had 2,880 checks in 24 hours (checking every 30 seconds) and 3 were down, your uptime would be:
(2877 / 2880) x 100 = 99.90%
Uptime Cards
On the monitor detail page, you'll see uptime cards showing:
- 24-hour uptime — last day
- 7-day uptime — last week
- 30-day uptime — last month
While data is loading, these cards show a loading spinner (not placeholder values).
What the Numbers Mean
| Uptime | Annual Downtime | Rating |
|---|---|---|
| 99.99% | About 52 minutes | Excellent |
| 99.9% | About 8.7 hours | Good |
| 99.5% | About 1.8 days | Acceptable |
| 99% | About 3.6 days | Needs improvement |
| Below 99% | Over 3.6 days | Poor |
Tips
- Most SLAs target 99.9% or higher
- Brief downtimes (caught and resolved quickly) have minimal impact on the percentage
- Blimey's monitoring is designed to provide accurate uptime data you can rely on