Calculator inputs
Example data table
Use this sample dataset to understand how the calculator compares reporting windows, downtime categories, and SLA performance.
| Period | Total Window | Recorded Downtime | Planned Downtime | Effective Downtime | Downtime % | Target |
|---|---|---|---|---|---|---|
| Week 1 | 7 days | 95 min | 20 min | 75 min | 0.7440% | 99.90% |
| Week 2 | 7 days | 36 min | 0 min | 36 min | 0.3571% | 99.90% |
| Month | 30 days | 220 min | 60 min | 160 min | 0.3704% | 99.95% |
Formula used
Downtime Percentage = (Effective Downtime ÷ Total Monitoring Period) × 100
Effective Downtime = Recorded Downtime − Planned Downtime, when planned time is excluded. Otherwise, effective downtime equals recorded downtime.
Uptime Percentage = 100 − Downtime Percentage
Allowed Downtime for Target = Total Monitoring Period × ((100 − Availability Target) ÷ 100)
These formulas help engineering and operations teams quantify reliability, compare periods, and evaluate performance against service commitments.
How to use this calculator
- Enter the full monitoring period and choose the correct unit.
- Enter total recorded downtime for that same period.
- Add planned downtime if maintenance windows should be separated.
- Choose whether planned downtime should be excluded.
- Set incident count, availability target, affected users, and loss rate.
- Click the calculate button to display results above the form.
- Use CSV or PDF export buttons for reports and reviews.
Frequently asked questions
1. What does downtime percentage measure?
It measures how much of the selected monitoring window was unavailable. A lower percentage means better reliability and stronger service continuity.
2. Should planned maintenance be included?
That depends on your reporting standard. Some teams exclude approved maintenance windows, while others include them for a stricter view of user impact.
3. How is uptime related to downtime?
Uptime is the remaining percentage after downtime is removed from one hundred percent. If downtime is 0.5%, uptime is 99.5%.
4. Why compare results against an availability target?
A target converts reliability goals into an allowed downtime threshold. That makes it easier to evaluate SLA performance for a week, month, or year.
5. What is MTBF in this calculator?
It is an approximate mean time between failures. The calculator estimates it by dividing available operating time by the number of incidents.
6. Can I use this for partial periods?
Yes. You can calculate downtime for hours, days, weeks, months, or years, as long as downtime and total period reference the same window.
7. What does estimated loss represent?
It multiplies effective downtime minutes by the cost per minute you enter. It gives a simple impact estimate for prioritization and reporting.