Uptime / Downtime Percentage & SLA Calculator
Convert downtime into uptime percentages, calculate allowed downtime for various SLA targets, and compute error budgets. Understand your service availability and SLA compliance at a glance.
Calculate Uptime, Downtime & SLA Metrics
Enter a time period and observed downtime to calculate uptime percentage, allowed downtime at various SLA targets, error budgets, and optional service credit estimates. This tool helps you understand SLA compliance and remaining error budget for your services.
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Understanding Uptime, Downtime & SLA
Service Level Agreements (SLAs) define the expected availability of a service, typically expressed as a percentage of uptime over a specific period. This calculator helps you understand how downtime translates to uptime percentages, error budgets, and SLA compliance.
Key Concepts
Uptime Percentage
The ratio of time a service is operational to the total measurement period. A 99.9% SLA means the service should be available 99.9% of the time.
Error Budget
The maximum amount of downtime allowed before breaching an SLA target. If you've used less than your allowed downtime, you have remaining error budget.
The Nines
Industry terminology for availability targets: "Two nines" = 99%, "Three nines" = 99.9%, "Four nines" = 99.99%, "Five nines" = 99.999%.
Service Credits
Many cloud providers offer service credits (partial refunds) when they fail to meet SLA commitments. Credit tiers vary by provider and uptime achieved.
Common SLA Targets & Allowed Downtime
| SLA Target | Per Day | Per Month (30d) | Per Year |
|---|---|---|---|
| 99% (Two nines) | 14m 24s | 7h 12m | 3d 15h 36m |
| 99.5% | 7m 12s | 3h 36m | 1d 19h 48m |
| 99.9% (Three nines) | 1m 26s | 43m 12s | 8h 46m |
| 99.95% | 43s | 21m 36s | 4h 23m |
| 99.99% (Four nines) | 8.6s | 4m 19s | 52m 34s |
| 99.999% (Five nines) | 0.86s | 26s | 5m 15s |
Formula Reference
Uptime % = (Total Period - Downtime) / Total Period * 100
Allowed Downtime = Total Period * (1 - SLA Target / 100)
Error Budget = Allowed Downtime - Actual Downtime
Considerations
- Planned maintenance may or may not count against SLA, depending on contract terms.
- Different providers measure downtime differently (e.g., per region, per service, per minute).
- SLAs often reset monthly, quarterly, or annually.
- Some SLAs only cover infrastructure availability, not application-level issues.
Important Disclaimer
This calculator is for educational and estimation purposes only. Actual SLA terms, credit calculations, and compliance determinations should be based on your specific service agreements and provider documentation. This tool does not provide legal, contractual, or financial advice.
Frequently Asked Questions
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