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Nines To Downtime Calculator

Work out nines to downtime instantly with clear inputs, formula shown and shareable results.

About Nines To Downtime Calculator

Allowed downtime is (1 - availability) multiplied by the period. The familiar landmarks follow directly: three nines gives 8.76 hours a year, four nines 52.6 minutes, and five nines just 5.26 minutes. Each additional nine cuts the allowance tenfold, which is why the cost of reliability grows so steeply at the top end.

Formula

Downtime from availability

downtime = (1 - availability) x period; 99.9% = 43.2 min/month, 99.99% = 4.32 min/month

Worked example

With the default values below, Nines To Downtime Calculator returns Allowed downtime of 262.80. Change any input above and every figure here is recalculated in your browser.

Inputs used

Availability targetaccepts 50–100 %
99.95 %
Periodone of Per day, Per week, Per month (30 days), Per quarter, Per year
Per year

Results

Allowed downtime
262.80 min
Allowed downtime in seconds
15,768.0 s
Allowed downtime in hours
4.380 h
Nines equivalent
3.3 nines over 365 days

Step by step

  1. 1Values used
  2. 2Downtime from availability
  3. 3Allowed downtime= 262.80 min
  4. 4Allowed downtime in seconds= 15,768.0 s
  5. 5Allowed downtime in hours= 4.380 h
  6. 6Nines equivalent= 3.3 nines over 365 days

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or fees or charges into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is five nines so expensive?

5.26 minutes a year leaves no room for a single manual intervention. Every failure must be handled automatically, which requires full redundancy at every layer including the ones you do not control.

Does the SLA period matter?

Enormously. Four nines measured monthly allows 4.3 minutes each month; measured annually it allows 52 minutes, which could all fall in one bad day.

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Nines To Downtime Calculator – Calculate Allowed downtime