ToolsUptime calculator
How much downtime does your target allow?
Enter an uptime target to see the allowed downtime for every period length, or enter downtime to get the percentage. The link reproduces the result.
Calculator
Target to downtime
Up to 6 decimal places.
Allowed downtime = period × (100 − target) / 100. Every figure is exact to the millisecond and rounded down, never up: rounding up would allow more downtime than the target does.
Allowed downtime at 99.9% in a 30-day month
43 min 12 s
| Day | 1 min 26.4 s1.44 min |
|---|---|
| Week | 10 min 4.8 s10.08 min |
| Month (28 days)February | 40 min 19.2 s40.32 min |
| Month (29 days)February in a leap year | 41 min 45.6 s41.76 min |
| Month (30 days)April, June, September, November | 43 min 12 s43.2 min |
| Month (31 days)The other seven months | 44 min 38.4 s44.64 min |
| Quarter (90 days)Q1 in a common year | 2 h 9 min 36 s129.6 min |
| Quarter (91 days)Q1 in a leap year, and Q2 | 2 h 11 min 2.4 s131.04 min |
| Quarter (92 days)Q3 and Q4 | 2 h 12 min 28.8 s132.48 min |
| Year (365 days)A common year | 8 h 45 min 36 s525.6 min |
| Year (366 days)A leap year | 8 h 47 min 2.4 s527.04 min |
Downtime to availability
Availability = (period − downtime) / period × 100, truncated to 6 decimals so a missed target never reads as met.
Availability over a month (30 days)
99.895833%
45 min of downtime in 30 days. Truncated to 6 decimals.
Method
How it is calculated.
Formula
Allowed downtime = period × (100 − target) / 100
Computed in whole milliseconds with exact integer arithmetic, then rounded down. A figure marked rounded down was not a whole millisecond; rounding up would promise more downtime than the target allows.
Months
28, 29, 30 and 31 days
Calendar months differ by up to three days, so each length is shown instead of an average. A 99.9% target allows 40 min 19.2 s in February and 44 min 38.4 s in a 31-day month.
Quarters
90, 91 and 92 days
Q1 has 90 days in a common year and 91 in a leap year, Q2 has 91, Q3 and Q4 have 92. Check which quarter your contract measures.
Years
365 days, or 366 in a leap year
A leap year adds a day of measured time and so a day's share of allowed downtime (86.4 s more at 99.9%).
Reverse
Availability = (period − downtime) / period × 100
Truncated to six decimals, never rounded up, so a missed target never reads as met. This is the same display rule Observer uses for SLA attainment.
Clock time
Elapsed time, not wall-clock time
A day is 24 hours of elapsed time. A period that spans a daylight saving change has an hour more or less on the wall clock, which some contracts count differently.