Uptime Percentage Calculator

Calculation mode

Incident mode helps security teams model outages by event frequency.

Measurement window

Choose the window you report for audits or SLAs.

Planned maintenance

Include planned maintenance in uptime window

Unplanned downtime

Exclude planned work to avoid misleading availability.

SLA target

%

Used to compute downtime allowance per period.

SLA period

Month uses an average length for consistency.

Reporting confidence (optional)

%

A note for teams using incomplete telemetry.

CSV/PDF exports use the latest computed result. Calculate first, then download.

Example data table

Scenario	Window	Planned	Unplanned	Include planned?	Uptime	Approx. nines
SIEM coverage	30 days	120 min	45 min	No	99.8958%	2.98
Control plane	7 days	60 min	20 min	No	99.8016%	2.70
Endpoint telemetry	24 hours	0 min	8 min	Yes	99.4444%	2.25

Values are illustrative. Your results depend on your window rules.

Formula used

Effective Window (minutes) = Measurement Window − Planned Maintenance (when excluded).

Uptime Percentage = ((Effective Window − Unplanned Downtime) / Effective Window) × 100

Incident-based Downtime = Incident Count × Average Incident Duration

Approximate Nines = −log10(1 − (Uptime% / 100))

How to use this calculator

Select a measurement window matching your reporting period.
Enter planned maintenance and choose whether to include it.
Pick total downtime or incident-based modeling.
Set an SLA target to see allowed downtime per period.
Click calculate to view results above the form.
Use CSV or PDF to share with stakeholders.

FAQs

1) Should planned maintenance count against uptime?

Many SLAs exclude planned maintenance to avoid penalizing scheduled work. Internal reliability dashboards often include it to show the full user-impact window.

2) What does “nines” mean?

“Nines” is a shorthand for reliability. For example, 99.9% is “three nines.” Higher nines mean less downtime and tighter operational discipline.

3) How does this help cybersecurity teams?

Security controls depend on consistent telemetry and service availability. Use uptime to quantify monitoring gaps, validate vendor claims, and support risk assessments.

4) What downtime should be counted as unplanned?

Count outages or degradations that reduce expected functionality, including failed updates, capacity issues, or control-plane incidents. Exclude planned windows if your policy allows it.

5) Can I model outages using incident data?

Yes. Choose incident mode and enter incident count and average duration. The calculator estimates downtime as count multiplied by average duration.

6) Why does the month allowance use an average month?

It uses an average month length to keep comparisons consistent. If you require strict calendar months, calculate with a day-based window for that exact month.

7) What if downtime exceeds the window?

The calculator caps unplanned downtime to the effective window to avoid negative uptime. If you see repeated caps, revisit the reporting window or your downtime inputs.

8) What is a good uptime target for critical systems?

It depends on threat models, business impact, and redundancy. Critical monitoring or control-plane services often target 99.9% or higher, paired with strong incident response.