Calculator Inputs
Use preset periods for quick entries, or switch to custom and enter exact monitored minutes from your logs or monitoring platform.
Example Data Table
| Service | Period | Planned Maintenance | Downtime | Target SLA | Actual Uptime | Status |
|---|---|---|---|---|---|---|
| API Gateway | 30-Day Month | 60 min | 25 min | 99.90% | 99.94205% | SLA Met |
| Auth Service | Week | 0 min | 20 min | 99.90% | 99.80159% | SLA Missed |
| Database Cluster | Quarter | 120 min | 45 min | 99.95% | 99.96525% | SLA Met |
| Notification Worker | 30-Day Month | 180 min | 65 min | 99.80% | 99.84891% | SLA Met |
Formula Used
1) Monitored Minutes
Monitored Minutes = Total Period Minutes − Planned Maintenance Minutes
2) Actual Uptime Percentage
Actual Uptime % = ((Monitored Minutes − Unplanned Downtime Minutes) ÷ Monitored Minutes) × 100
3) Allowed Downtime
Allowed Downtime = Monitored Minutes × (1 − Target SLA ÷ 100)
4) Error Budget Remaining
Error Budget Remaining = Allowed Downtime − Unplanned Downtime
5) MTTR and MTBF
MTTR = Unplanned Downtime ÷ Incident Count
MTBF = Uptime Minutes ÷ Incident Count
This page uses a common monitoring approach. Some contracts define exclusions, maintenance windows, and credits differently.
How to Use This Calculator
- Select a preset period or choose custom.
- Enter total minutes for the reporting window.
- Add planned maintenance minutes, if excluded by contract.
- Enter unplanned downtime minutes from your incident logs.
- Add incident count to estimate MTTR and MTBF.
- Set your target SLA percentage, such as 99.9.
- Enter monthly fee if you want a credit estimate.
- Click the calculate button to show results above the form.
- Use the CSV or PDF buttons to export the report.
FAQs
1) What does SLA uptime mean?
SLA uptime is the percentage of monitored service time that stayed available during a reporting period. It is usually measured after subtracting approved exclusions, such as planned maintenance windows.
2) Why subtract planned maintenance from the total period?
Many contracts exclude approved maintenance windows from uptime calculations. Removing those minutes creates monitored time, which is the duration actually judged against the SLA commitment.
3) What is the difference between downtime and allowed downtime?
Downtime is the service interruption you actually recorded. Allowed downtime is the maximum interruption your target SLA permits before the service misses its contractual availability target.
4) What is an error budget?
An error budget is the downtime your service can still consume while staying within the target. Positive remaining budget means you still have room. Negative values mean the target was exceeded.
5) Are the credit results contract-accurate?
Not always. The credit output is an example estimate based on the selected policy. Real contracts often define separate thresholds, exclusions, caps, and claim procedures that you must verify manually.
6) Which period should I choose?
Choose the same reporting window used in your agreement. Monthly SLA reviews often use a month, while internal engineering reviews may use weekly or quarterly periods. Use custom for exact audit windows.
7) What happens if downtime exceeds allowed downtime?
The calculator shows a negative error budget and marks the SLA as missed. That indicates the measured uptime fell below the target and may trigger internal escalation or service credit review.
8) Can I use this for vendor comparisons?
Yes. It helps compare uptime performance, downtime tolerance, and possible billing impact across providers. Just keep the same period, exclusion rules, and credit assumptions for every vendor reviewed.