UptimeTea
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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.

UptimeNinesDailyWeeklyMonthlyYearly
one nine2h 24m16h 48m3d 1h36d 13h
—1h 12m8h 24m1d 13h18d 6h
two nines14m 24s1h 41m7h 18m3d 16h
—7m 12s50m 24s3h 39m1d 20h
three nines1m 26s10m 5s43m 50s8h 46m
—43.2s5m 2s21m 55s4h 23m
four nines8.6s1m4m 23s52m 36s
—4.3s30.2s2m 11s26m 18s
five nines0.86s6s26.3s5m 16s
six nines0.09s0.60s2.6s31.6s

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

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.

Explore more

Status pages

Publish the uptime you measure on a white-label status page your customers can check.

Response time monitoring

Uptime says whether the site answered. Response time says how fast. Track both every minute.

Multi-location monitoring

Checks re-verified from independent locations, so one flaky network never counts against your SLA.

For agencies

Monitor every client site under your own brand and prove the uptime you promised in the contract.

Stop estimating. Measure your real uptime.

UptimeTea checks your sites every minute from multiple locations and puts the actual percentage on a status page you can share. 50 monitors free, no credit card.