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Uptime Downtime

Free Uptime Downtime calculator with clear step-by-step results.

About Uptime Downtime

Converts an availability target into a concrete error budget in minutes, tracks what has been spent, and derives mean time to restore from incident count. Framing availability as a budget rather than a promise is what makes it possible to trade reliability against release velocity.

Formulas

Error budget

Allowed minutes = period days x 1440 x (1 - uptime target)

Mean time to restore

MTTR = total downtime minutes / number of incidents

Worked example

With the default values below, Uptime Downtime returns Downtime allowed by the target of 43.20. Change any input above and every figure here is recalculated in your browser.

Inputs used

Uptime targetaccepts 50–100 %
99.9 %
Measurement periodaccepts 1–366 days
30 days
Incidents in the periodaccepts 0–500
2
Downtime actually incurredminimum 0 min
55 min

Results

Downtime allowed by the target
43.20 min
Error budget remaining
-11.80 min
Uptime actually achieved
99.8727% %
Mean time to restore
27.50 min

Step by step

  1. 1Values used
  2. 2Error budget
  3. 3Mean time to restore
  4. 4Downtime allowed by the target= 43.20 min
  5. 5Error budget remaining= -11.80 min
  6. 6Uptime actually achieved= 99.8727 %
  7. 7Mean time to restore= 27.50 min

Assumptions and limits

  • The result is derived only from the 4 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 4 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

How much downtime does 99.9% allow?

About 43.2 minutes per 30-day month, or 8.76 hours a year. Each additional nine divides that by ten - 99.99% allows just 4.3 minutes a month.

What if the budget is exhausted?

The usual convention is to freeze feature releases and spend engineering effort on reliability until the budget recovers in the next window.

Related Calculators

Uptime Downtime – Calculate Downtime allowed by the target