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Reliability & Operations

SLA / Uptime Calculator

Translate an availability percentage into a downtime allowance for a chosen period.

Calculations run in your browser. The tool does not send your inputs to a server.

01Your inputs

Local workspace

Start with the sample below, or enter your own values.

Enter a percentage as a number, such as 85 for 85%.
Enter a numeric value using the unit shown in the label.

02Your result

Your result will appear here. Choose an action after checking your inputs.

A quick guide

How to use this tool

  1. Check the example and the unit beside each input.
  2. Enter your values and choose Calculate.
  3. Review the result and assumptions, then copy what you need.

Reset example restores the starting values. Clear removes text and number inputs, returns choices to their first valid option, and removes the result.

Reference guide

Explanation and worked examples

99.9% over 30 days permits 43.2 minutes of downtime. This does not account for contractual exclusions or maintenance terms.

Use in day-to-day IT work

Prepare an availability review, recovery exercise or operational handover.

Checks before applying the result

  • Use the same measurement period, service boundary and timezone throughout the exercise.
  • Compare targets with observed incidents and timed recovery tests, including dependencies and escalation time.
New to the terminology?
SLA
A service agreement that defines a target and how it is measured.
RTO
Recovery Time Objective: how quickly service must be restored.
RPO
Recovery Point Objective: how much recent data loss is acceptable.

Keep exploring

Combined SLA CalculatorMTBF / MTTR CalculatorRTO / RPO PlannerMaintenance Window Calculator

How calculations work and where the models stop →