Uptime and SLA downtime calculator

Turn an uptime percentage into the minutes of downtime it allows, spend the budget on real outages, and see what your check interval can and cannot prove. It runs in your browser; nothing you type is sent anywhere.

Allowed downtime

A 99.9% target allows 43 min 50 s of downtime per month.

Spend the budget

2 outages used 35 min. You have 8 min 50 s left.

What your check interval can prove

A check every 5 min can miss an outage shorter than 5 min entirely, and measures downtime in steps of 5 min. Your whole budget is about 8 check intervals.

Common targets

Allowed downtime for common uptime targets
UptimePer dayPer weekPer monthPer year
99%14 min 24 s1 h 40 min 48 s7 h 18 min 18 s3 d 15 h 39 min
99.5%7 min 12 s50 min 24 s3 h 39 min 9 s1 d 19 h 49 min
99.9%1 min 26 s10 min 5 s43 min 50 s8 h 45 min 58 s
99.95%43 s5 min 2 s21 min 55 s4 h 22 min 59 s
99.99%9 s1 min4 min 23 s52 min 36 s
99.999%< 1 s6 s26 s5 min 16 s

How it is calculated

Allowed downtime = period length × (1 − uptime ÷ 100). A year is taken as 365.25 days (31,557,600 seconds) and a month as one twelfth of that, 30.4375 days (2,629,800 seconds). A calculator that assumes a 30-day month gives 38 seconds less for 99.9%, so two tools can disagree without either being wrong; check which month your contract defines.

The budget is per period and shared by every incident: three short outages spend it exactly as one long one does. Contracts also decide what does not count, such as scheduled maintenance; this calculator counts all the minutes you enter.

Measuring a figure like 99.99% needs a probe that runs more often than the budget is long. SoloNOC derives uptime from ping history collected by its on-site agent; see how it keeps an upstream failure from becoming forty pages.

More from SoloNOC

SoloNOC is network monitoring for the one-person IT shop and the small MSP: one agent per site, flat plans, a 14-day trial with no card. Start free.