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Uptime / SLA calculator How much downtime does 99.9% allow?
Type an uptime percentage and see the downtime it permits per day, week, month and year. Or start from the minutes you were down and get the uptime percentage back.
Uptime percentage to allowed downtime
99.9% uptime means 0.1% downtime.
- Daily
- 1m 26s
- Weekly
- 10m 5s
- Monthly
- 43m 50s
- Quarterly
- 2h 11m
- Yearly
- 8h 46m
Downtime to uptime percentage
Had an outage? Enter how long you were down and the period your SLA is measured over.
Resulting uptime
99.931554%
SLA uptime tiers and the downtime they allow
The "nines" shorthand counts the nines in the percentage. Each extra nine cuts the allowed downtime by ten, and roughly multiplies the engineering cost of reaching it.
| Uptime | Nines | Daily | Weekly | Monthly | Yearly |
|---|---|---|---|---|---|
| one nine | 2h 24m | 16h 48m | 3d 1h | 36d 13h | |
| — | 1h 12m | 8h 24m | 1d 13h | 18d 6h | |
| two nines | 14m 24s | 1h 41m | 7h 18m | 3d 16h | |
| — | 7m 12s | 50m 24s | 3h 39m | 1d 20h | |
| three nines | 1m 26s | 10m 5s | 43m 50s | 8h 46m | |
| — | 43.2s | 5m 2s | 21m 55s | 4h 23m | |
| four nines | 8.6s | 1m | 4m 23s | 52m 36s | |
| — | 4.3s | 30.2s | 2m 11s | 26m 18s | |
| five nines | 0.86s | 6s | 26.3s | 5m 16s | |
| six nines | 0.09s | 0.60s | 2.6s | 31.6s |
How uptime is calculated
Uptime is the share of a period during which the service worked:
uptime % = (period − downtime) ÷ period × 100
This page uses a 365.25-day year, so a month is 30.4375 days and a quarter is 91.31 days. Monthly, quarterly and yearly figures therefore add up.
SLA, SLO and SLI in one breath
- SLI, service level indicator: the measurement, such as the percentage of checks that returned 200 within 5 seconds.
- SLO, service level objective: the target you hold yourself to internally, usually stricter than what you sell.
- SLA, service level agreement: the contract with customers, with credits or penalties when the SLO is missed.
Frequently asked questions
Didn't find your answer? Email support@uptimetea.com.
How much downtime is 99.9% uptime?
99.9% uptime allows about 1m 26s of downtime a day, 10m 5s a week, 43m 50s a month and 8h 46m a year. It is the most common SLA for business SaaS and hosting.
How much downtime is 99.99% uptime?
99.99% uptime, or four nines, allows about 8.6 seconds a day, 4m 23s a month and 52m 36s a year. Reaching it usually needs redundancy across regions and automated failover.
What is the difference between an SLA, an SLO and an SLI?
An SLI is the measurement, for example the percentage of successful checks. An SLO is the internal target you set for that measurement. An SLA is the external promise to customers, usually with credits or refunds if you miss it.
Why does the monthly figure differ from the yearly figure divided by 12?
It does not. This calculator uses a 365.25-day year and a 30.4375-day average month, so monthly and yearly figures are consistent. Some calculators use a 30-day month, which makes their monthly figure about 1.4% smaller.
Does scheduled maintenance count as downtime?
Most SLAs exclude announced maintenance windows, but the wording matters. Read the SLA for how much notice is required and whether there is a cap on maintenance hours. UptimeTea lets you schedule maintenance windows so alerts and status pages reflect it.
How do I know my real uptime?
Measure it from outside your own infrastructure. An uptime monitor checks your site every minute from several locations and records every failed check, so the percentage on your status page is evidence, not a guess.
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