Tool
Uptime Budget Calculator
An availability target is a downtime budget written as a percentage. This converts it into minutes for the window you care about, then spends real incidents against it.
Run it
Uptime Budget Calculator
Method
From percentage to minutes
The window in minutes multiplied by the shortfall from 100%. Everything else follows: hours, minutes per day, and how many incidents of a given length the budget absorbs.
Method
Spending the budget
Incidents multiplied by mean recovery time is what has been used. Subtracting that from the allowance turns an abstract target into a remaining balance, which is the form it is actually managed in.
The honest part
What the number does not cover
A budget in minutes says nothing about when the minutes fall or who they hit. Five minutes across a quiet night and five in the middle of a launch are the same figure and not the same event. Availability targets also depend on how you define an outage in the first place, which is a decision this cannot make for you.
Asked often
Common questions
Why is the target an input rather than a preset?
Because availability targets are commitments particular to a service and a contract. Hard-coding a familiar figure would suggest an authority the tool does not have.
Should I use mean recovery time or worst case?
Run both. The gap between them is the range your budget actually sits in, and if the worst case blows the budget on a single incident, that is the finding.
Does planned maintenance count?
Only if your definition of an outage includes it, and definitions differ. Decide once and apply it consistently, or the figures will not compare across windows.