Uptime & SLA Calculator
Convert an SLA percentage into real allowed downtime, or calculate the uptime you actually achieved from total outage time in a period.
1. SLA → allowed downtime
2. Total downtime → actual uptime
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Allowed downtime by SLA level
| Uptime | Per day | Per month (30 days) | Per year |
|---|---|---|---|
| 99% | 14 min 24 sec | 7 hr 12 min | 3 days 15 hr 36 min |
| 99.5% | 7 min 12 sec | 3 hr 36 min | 1 day 19 hr 48 min |
| 99.9% | 1 min 26 sec | 43 min 12 sec | 8 hr 45 min |
| 99.95% | 43 sec | 21 min 36 sec | 4 hr 22 min |
| 99.99% | 9 sec | 4 min 19 sec | 52 min 34 sec |
| 99.999% | < 1 second | 26 sec | 5 min 15 sec |
Reading an SLA correctly
- Measurement period: monthly or yearly. 99.9% per year allows a single 8-hour outage, while 99.9% per month does not.
- Definition of downtime: whether it counts only total unavailability, or also includes degraded performance and packet loss.
- Exclusions: scheduled maintenance, customer-caused incidents, and force majeure.
- Compensation: the service credit for each breach level and the deadline for submitting a claim.
Frequently asked questions
What is an uptime SLA?
An uptime SLA (Service Level Agreement) is a provider’s written commitment to the percentage of time a service will be available over a given period, usually per month. If the target is missed, customers are typically entitled to compensation such as service credits, as defined in the contract.
How much downtime does 99.9% uptime allow?
About 43 minutes 12 seconds per month (30 days), or about 8 hours 46 minutes per year.
What do "three nines" and "four nines" mean?
They refer to the number of 9s in the uptime percentage. Three nines = 99.9%, four nines = 99.99%, five nines = 99.999%. Each additional 9 cuts the allowed downtime to one tenth.
Does scheduled maintenance count as downtime?
It depends on the contract. Many SLAs exclude scheduled maintenance that is announced in advance. Always check the SLA’s definition of downtime, how it is measured, and the procedure for claiming credits.
How do I combine the SLAs of several components?
If a service depends on several components in series (for example, internet connectivity and a server), the combined uptime is roughly the product of each. Two components at 99.9% give about 99.8%. Redundancy (two parallel paths) raises the combined uptime instead.
Need infrastructure you can rely on?
Talk to the Cloudku team about your uptime and redundancy requirements for colocation or IP transit.