SLA Uptime Calculator
How much downtime does your SLA actually allow?
Quick reference
| SLA | Per month | Per year |
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SLA, SLO, SLI; What's the difference?
SLI (Service Level Indicator)
The actual measurement. A ratio of good events to total events over a time window. Example: 99.95% of requests returned successfully in the last 30 days.
SLO (Service Level Objective)
Your internal target for an SLI. "We aim for 99.9% availability" is an SLO. Miss it and your team gets paged. It's a threshold you set for yourself.
SLA (Service Level Agreement)
A contract with your customers. If you promise 99.9% uptime in your SLA and miss it, you owe credits or refunds. SLAs are typically looser than SLOs, so you want a buffer before contractual penalties kick in.
In practice: You measure SLIs, set internal SLOs tighter than your public SLA, and only burn error budget when SLIs drop below SLO thresholds. If your SLA is 99.9%, your SLO might be 99.95% or higher so you have margin before customers notice.
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