Uptime & SLA downtime calculator
Enter an uptime percentage to see how much downtime it allows, or enter downtime to get the uptime percentage. 99.9% uptime allows 43 minutes 12 seconds of downtime per 30-day month.
43 min 12 s
| Period | Allowed downtime | Required uptime |
|---|---|---|
| Day | 1 min 26 s | 23 h 58 min |
| Week | 10 min 4 s | 6 d 23 h |
| Month (30 days) | 43 min 12 s | 29 d 23 h |
| Quarter | 2 h 11 min | 91 d 3 h |
| Year (365 days) | 8 h 45 min | 364 d 15 h |
The “nines” table
Allowed downtime for common uptime percentages, calculated with a 30-day month, 91.25-day quarter and 365-day year.
| Uptime | Per day | Per week | Per month (30 days) | Per quarter | Per year (365 days) |
|---|---|---|---|---|---|
| 90% | 2 h 24 min | 16 h 48 min | 3 d | 9 d 3 h | 36 d 12 h |
| 95% | 1 h 12 min | 8 h 24 min | 1 d 12 h | 4 d 13 h | 18 d 6 h |
| 99% | 14 min 24 s | 1 h 40 min | 7 h 12 min | 21 h 54 min | 3 d 15 h |
| 99.5% | 7 min 12 s | 50 min 24 s | 3 h 36 min | 10 h 57 min | 1 d 19 h |
| 99.9% | 1 min 26 s | 10 min 4 s | 43 min 12 s | 2 h 11 min | 8 h 45 min |
| 99.95% | 43.2 s | 5 min 2 s | 21 min 36 s | 1 h 5 min | 4 h 22 min |
| 99.99% | 8.64 s | 1 min | 4 min 19 s | 13 min 8 s | 52 min 33 s |
| 99.995% | 4.32 s | 30.2 s | 2 min 9 s | 6 min 34 s | 26 min 16 s |
| 99.999% | 0.86 s | 6.05 s | 25.9 s | 1 min 18 s | 5 min 15 s |
Background: uptime percentages explained · SLA, SLO and SLI explained
Frequently asked questions
How much downtime does 99.9% uptime allow?
99.9% uptime ("three nines") allows 1 minute 26 seconds of downtime per day, 10 minutes 4 seconds per week, 43 minutes 12 seconds per 30-day month and 8 hours 45 minutes 36 seconds per 365-day year.
How much downtime is 99.99% uptime?
99.99% uptime ("four nines") allows about 8.6 seconds of downtime per day, 4 minutes 19 seconds per 30-day month and 52 minutes 33.6 seconds per year.
How do you calculate uptime percentage?
Uptime percentage = (total time − downtime) ÷ total time × 100. For example, 30 minutes of downtime in a 30-day month (43,200 minutes) is (43,200 − 30) ÷ 43,200 × 100 = 99.93% uptime.
What is the difference between 99.9% and 99.99% uptime?
Each extra nine cuts allowed downtime by a factor of ten: 99.9% permits about 8.8 hours of downtime a year, while 99.99% permits about 53 minutes. Reaching more nines usually requires redundancy, automated failover and fast detection.
Should maintenance count as downtime?
It depends on your SLA. Many agreements exclude scheduled maintenance announced in advance. Uptime Tracker lets you schedule maintenance windows that suppress alerts and are excluded from availability, so your reports match how your SLA counts time.
How do I measure my real uptime?
Use an uptime monitor that checks your service at a short, fixed interval and confirms failures before recording downtime. Uptime Tracker checks every 30 seconds to 5 minutes and reports time-weighted availability per monitor, and there is a free plan.
Measure your real uptime, free
Uptime Tracker checks your site every 30 seconds to 5 minutes, confirms failures and reports time-weighted availability. Start free.
- Free forever plan
- No credit card
- Cancel anytime