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Server Uptime SLA Calculator

Convert uptime SLA percentages into allowed downtime for a selected reporting period.

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Inputs

%
days

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Results

Allowed Downtime
Allowed Downtime43.2
Allowed Downtime2,592
Required Uptime719.28

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Assumptions

  • The period is measured as continuous calendar days.
  • This calculator does not interpret maintenance windows, service credits, exclusions, or contract language.
  • Results are calculated locally and are for planning only.

Sensitivity preview

Uptime Target -10%: Allowed Downtime 3d 0h 38m 53s

Uptime Target Current: Allowed Downtime 43m 12s

Uptime Target +10%: Allowed Downtime Invalid input

Formula: Allowed downtime = (1 - uptime percent / 100) * period days * 24 hours.

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About this Server Uptime SLA Calculator

Availability percentages can be hard to interpret. This calculator turns an SLA such as 99.9% or 99.99% into an allowed downtime window.

Who this calculator is for

  • SRE, DevOps, and IT operations teams.
  • SaaS teams comparing vendor availability commitments.
  • Managers translating uptime targets into incident budgets.

When to use it

  • Convert 99.9% uptime into monthly allowed downtime.
  • Compare SLA levels before choosing a hosting or SaaS vendor.
  • Estimate downtime budget for a service reliability target.

How to use this calculator

  1. Enter the target uptime percentage.
  2. Enter the reporting period length in days.
  3. Review allowed downtime in plain English, minutes, and seconds.

Key assumptions

  • The period is measured as continuous calendar days.
  • This calculator does not interpret maintenance windows, service credits, exclusions, or contract language.
  • Results are calculated locally and are for planning only.

Accuracy and testing

Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.

View accuracy page

How this calculator works

Allowed downtime minutes = (1 - Uptime percent / 100) x Period days x 24 x 60. Uptime hours = Total period hours - downtime hours.
Allowed downtime = (1 - uptime percent / 100) * period days * 24 hours.

Inputs explained

Uptime percentage

The availability target or SLA level, such as 99.9 or 99.99.

Period days

The measurement window used by the SLA, such as 30 days or 365 days.

Understanding your results

The allowed downtime is the total unavailability budget for the selected period. Real contracts may define exclusions, maintenance windows, and credit rules separately.

Example scenarios

99.9% monthly SLA

A 30-day month at 99.9% uptime allows about 43 minutes and 12 seconds of downtime.

Key Features

  • Instant Calculation
  • Private & Secure
  • Mobile Optimized

Tips & Best Practices

  • Use the same reporting period your SLA uses.
  • Pair uptime budgets with downtime cost estimates.
  • Separate planned maintenance from unplanned downtime only if your SLA does.

Frequently Asked Questions

How much downtime is 99.9% uptime per month?
For a 30-day month, 99.9% uptime allows about 43 minutes and 12 seconds of downtime.
Does this calculate service credits?
No. Service credits depend on contract language, exclusions, severity definitions, and claim processes.
Are uptime targets stored?
No. The calculation runs locally in your browser.