Website Uptime Calculator
This calculator turns a measured reporting window and its downtime into an availability percentage. It is useful for comparing monitoring windows when the definition of downtime is consistent.
How to use this calculator
- Enter a positive reporting duration and downtime within that period.
- Check that the input values use the same units and reporting period before comparing scenarios.
- Change one assumption at a time to see which input drives the result.
Formula and method
Uptime (%) = (reporting hours − downtime hours) / reporting hours × 100.
- (720 − 2) ÷ 720 × 100 ≈ 99.72%.
- The number is only as reliable as the monitoring coverage and your downtime definition. It does not establish a provider SLA or customer impact.
Worked examples
Worked example
A 30-day reporting window has 720 hours; monitoring recorded 2 hours of downtime.
(720 − 2) ÷ 720 × 100 ≈ 99.72%.
The observed uptime is about 99.72% for the supplied window.
Understanding the result
The observed uptime is about 99.72% for the supplied window.
The number is only as reliable as the monitoring coverage and your downtime definition. It does not establish a provider SLA or customer impact.
Important notes
Enter a positive reporting duration and downtime within that period.
The displayed result uses the entered assumptions; validate important estimates against source measurements, specifications or qualified guidance.
Frequently asked questions
Does this verify an SLA?
No. Compare monitoring evidence with the exact SLA definition, exclusions and measurement source.
Can partial outages be counted?
Yes, if your monitoring policy defines how partial service degradation contributes to downtime.
Affiliate recommendations
Tools related to Website Uptime Calculator
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Related explanations
Learn the method behind the number or compare the terminology before using the calculator.
- How to Calculate Percentage Change — Learn the percentage change formula, how to calculate increases and decreases, and why the original value matters.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.