Free tool
Uptime & SLA calculator
Enter an uptime percentage to see how much downtime it allows, or enter downtime to get your uptime %. Free, no sign-up.
Allowed downtime for an uptime target
Uptime % from downtime
SLA reference
Downtime allowed by common SLA levels
| Uptime | Per day | Per week | Per month | Per quarter | Per year |
|---|---|---|---|---|---|
| 99% | 14m 24s | 1h 40m 48s | 7h 18m 18s | 21h 54m 54s | 3d 15h 39m 36s |
| 99.5% | 7m 12s | 50m 24s | 3h 39m 9s | 10h 57m 27s | 1d 19h 49m 48s |
| 99.9% | 1m 26s | 10m 5s | 43m 50s | 2h 11m 29s | 8h 45m 58s |
| 99.95% | 43s | 5m 2s | 21m 55s | 1h 5m 45s | 4h 22m 59s |
| 99.99% | 9s | 1m | 4m 23s | 13m 9s | 52m 36s |
| 99.999% | 1s | 6s | 26s | 1m 19s | 5m 16s |
Guide
How to use uptime targets
- Pick an SLA you can keep. 99.9% leaves about 43 minutes a month for incidents and maintenance; 99.99% leaves about 4 minutes.
- Decide whether scheduled maintenance counts. Many SLAs exclude announced maintenance windows, so announce maintenance properly.
- Measure it. Endpoint monitoring tells you when a service is down and for how long.
- Show it. A public status page with uptime history builds trust and cuts “is it down?” tickets. See the status page glossary for SLA, SLO and SLI.
Uptime calculator FAQ
How much downtime is 99.9% uptime?
99.9% uptime (“three nines”) allows about 1m 26s of downtime per day, 43m 50s per month and 8h 45m 58s per year.
How much downtime is 99.99% uptime?
99.99% uptime (“four nines”) allows about 9s per day, 4m 23s per month and 52m 36s per year.
How do you calculate uptime percentage?
Uptime % = (total time − downtime) ÷ total time × 100. For example, 30 minutes of downtime in a 30-day month is (43,200 − 30) ÷ 43,200 × 100 = 99.93%.
What is the difference between an SLA, SLO and SLI?
An SLI is what you measure (for example, successful requests). An SLO is your internal target for it (99.95%). An SLA is the promise you make to customers (99.9%), usually with credits if you miss it.
How should I show uptime to customers?
A public status page with an uptime history per service shows customers your real availability and where to find updates during an incident.
Track and show your uptime.
Statusentry gives you a public status page with uptime history, and endpoint monitoring from $9.99/month. Start free.