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SLA / Uptime calculator
Convert SLA availability percentages to exact downtime per year, month, week and day. Enter 99.95% and instantly see that it means about 4 hours 23 minutes of allowed downtime per year.
%
Enter guaranteed uptime (SLA) in percent, e.g. 99.95
| Period | Days | Hours | Minutes | Seconds | Total (human-readable) |
|---|
Calculation: downtime = (1 - uptime/100) × period duration. A year is 365 days, a month is 30 days.
What it is
Uptime shows how long a system or service stays available. The tool converts availability percentage to real downtime and vice versa.
How it works
Enter a target availability (e.g., 99.9%) or a period length. The calculator instantly returns the expected downtime.
Examples
- 99.9% per month: ≈ 43 minutes of downtime.
- 99.99% per week: ≈ 1 minute.
- 43 minutes/month → availability: ≈ 99.9%.
Limitations & notes
Results are estimates. Actual downtime depends on maintenance windows, incidents and timezone. Use monitoring logs for audits.
FAQ
- What does 99.9% uptime mean in practice? An SLA of 99.9% allows approximately 8 hours 46 minutes of downtime per year, or about 43 minutes per month. Each additional nine dramatically reduces the allowed outage - 99.99% permits only 52 minutes per year.
- Why do calculated numbers differ between sources? Different tools may use different assumptions: a 365-day year vs 365.25, a 30-day month vs calendar months, and rounding precision. This calculator uses 365 days per year and 30 days per month for consistency.
- What is the difference between SLA and SLO? SLA (Service Level Agreement) is a contractual commitment to a minimum uptime percentage, often with financial penalties for breaches. SLO (Service Level Objective) is an internal target that teams set for themselves, typically stricter than the SLA, to provide a safety margin.
- How do I choose the right uptime target? Consider the cost of downtime versus the cost of redundancy. Most web services target 99.9% (three nines). Critical infrastructure like payment processing or healthcare may require 99.99% or higher, which demands redundant systems, failover mechanisms and on-call engineering teams.