Uptime reference

99% uptime two nines

Two nines is where availability starts being written into contracts. It still allows over seven hours down per month, which is a full working day of outage per quarter.

7h 12m of downtime allowed per month

99% uptime by period

A month is taken as 30 days, a quarter as 90 days and a year as 365 days.

Period	Allowed downtime	Required uptime
Per day	14m 24s	23h 45m
Per week	1h 40m	6d 22h
Per month	7h 12m	29d 16h
Per quarter	21h 36m	89d 2h
Per year	3d 15h	361d 8h

Where 99% is used

A common entry-level commitment for smaller vendors, internal platforms, and the cheaper tier of a tiered SLA. It is the level most teams hit by accident once they have basic monitoring and someone who responds.

What it demands

Business-hours response is enough. You can absorb a multi-hour incident and still make the number. The failure mode at this tier is not slow recovery, it is not noticing at all over a weekend.

One step either way

Dropping to 95% widens the monthly budget to 1d 12h. Moving up to 99.5% cuts it to 3h 36m.

Measuring it

You cannot report on a service level you are not measuring at a finer resolution than the budget itself. At 99% the monthly allowance is 7h 12m, so a check interval anywhere near that figure will miss breaches entirely. Work out your own numbers, or monitor it continuously from four regions, free to start.

Other service levels

Compare the tiers

Every common service level, and the downtime each one allows per month.

90% 3d / month one nine 95% 1d 12h / month 99.5% 3h 36m / month 99.9% 43m 12s / month three nines 99.95% 21m 36s / month 99.99% 4m 19s / month four nines 99.999% 26s / month five nines

Calculators: Uptime calculator · SLA calculator · Downtime calculator · Availability calculator · Downtime cost calculator

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