Uptime and Downtime Calculator

How to use the Uptime and Downtime Calculator

1. 1Enter an uptime percentage, or minutes of downtime and a period.
2. 2Pick the units or options from the menus if the uptime tool offers them.
3. 3Read the uptime in the large result box.
4. 4Look at the extra rows for related figures.
5. 5Press Copy result to keep the answer.

When you need the uptime

Engineers, IT managers and customers use it to set and check service level agreements.

Each extra nine cuts the allowed downtime tenfold but costs far more to achieve. Scheduled maintenance often does not count against an SLA, so read the exclusions.

How the uptime is worked out

Allowed downtime = (1 − uptime) × the length of the period. A year is 365.25 days, or 525,960 minutes. 99.9% uptime ('three nines') allows about 8 hours 46 minutes of downtime a year. 99.99% allows about 52.6 minutes, and 99.999% about 5.3 minutes. 43 minutes down in a month is 99.9019% uptime.

Every answer on this page comes from that one rule, so you can check any result by hand with a calculator. The figures shown underneath, such as other units, are conversions of the same answer.

• Day, week, month, year
• Reverse calculation
• Readable times

Mistakes to avoid with uptime

A month is not always 30 days, so the tool uses the average month. Check how your contract defines the measuring period.

On phone and computer

On a phone, type into the boxes one after another and read the uptime underneath; Copy result puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the uptime move. The uptime and downtime calculator works the same on both.

Checking your uptime by hand

A good habit is to test the uptime and downtime calculator with a case you already know. 99.9% uptime ('three nines') allows about 8 hours 46 minutes of downtime a year. 99.99% allows about 52.6 minutes, and 99.999% about 5.3 minutes. 43 minutes down in a month is 99.9019% uptime.

If your own figures give a surprising answer, repeat the working yourself: Allowed downtime = (1 − uptime) × the length of the period. A year is 365.25 days, or 525,960 minutes. Small differences usually come from rounding, from mixing units, or from a typing slip in one of the inputs. Uptime targets are easier to understand as time. Count the gap between dates with Days Between Dates, work with the Percentage Calculator for rates, and see time across places with the Time Zone Converter.

Features

• Average month length
• Read the SLA exclusions
• Each nine is ten times stricter
• Clear messages when the uptime inputs make no sense
• Copy the result with one tap
• Private: nothing is uploaded

Frequently asked questions