This calculator turns an availability or uptime target, such as 99.9% (“three nines”), into the downtime it allows. You get the downtime per year, per 30-day month, per week and per day.
Formula
Availability = uptime ÷ total time, so allowed downtime = (1 − availability) × period. A 365-day year is 8,760 hours, a 30-day month is 43,200 minutes, a week is 10,080 minutes and a day is 86,400 seconds.
- a: the availability target in percent
Worked Example
A 99.9% target.
- 1 − 0.999 = 0.001
- Year: 0.001 × 8760 = 8.76 h
- Month: 0.001 × 43,200 = 43.2 min
- Week: 0.001 × 10,080 = 10.08 min
- Day: 0.001 × 86,400 = 86.4 s
Limits and common mistakes
- Each extra nine cuts downtime tenfold: 99.99% allows 52.6 min a year, 99.999% about 5.3 min.
- Agreements differ on what counts (planned maintenance, partial outages) and on the measuring window; read the definition.
- A month of 31 days allows a little more downtime than the 30-day figure.
Formula used
in a | Availability target | % | 99.9 | 0 | 100 out yr | Downtime per year (365 days) | h | (1 - a / 100) * 8760 | 2 out mo | Downtime per 30-day month | min | (1 - a / 100) * 43200 | 1 out wk | Downtime per week | min | (1 - a / 100) * 10080 | 2 out dy | Downtime per day | s | (1 - a / 100) * 86400 | 1
Each line is one input (in, sel, list) or one result (out: label, unit, formula, decimals). How the calculators work
Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.
More cards in this drawer
- Freight Transportation Cost Calculator: Estimate Shipping25.00 USD
- Conveyor Belt Feet per Minute Calculator and Formula100.00 ft/min
- Visits per 1,000: Formula and Examples50.00 visits per 1,000
- Welding Inches per Minute Calculator and Formula6.00 in/min
- Average Sales Price Calculator Formula and Examples100.00 $/unit
- Freight Shipping Weight Calculator: How It Works500 lb