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Availability Calculator – SLA Uptime & Downtime
Calculate availability and downtime based on your SLA or SLO. Use our availability calculator and cheat sheet to see uptime/downtime data based on hours, days, weeks, months, quarters, and years!
SREs, DevOps, and engineering leaders rely on availability targets to define SLAs and SLOs. This cheat sheet breaks down downtime allowances at each availability level from 90% to 99.999% so you can plan, benchmark, and communicate expectations with clarity.
Availability Cheat Sheet
| Availability level | Downtime per year | Downtime per quarter | Downtime per month | Downtime per week | Downtime per day | Downtime per hour |
|---|---|---|---|---|---|---|
| 90% | 36.52 days | 9.12 days | 3.05 days | 16.79 hours | 2.39 hours | 6.01 minutes |
| 95% | 18.25 days | 4.58 days | 1.52 days | 8.41 hours | 1.21 hours | 3.01 minutes |
| 99% | 3.65 days | 21.92 hours | 7.31 hours | 1.69 hours | 14.41 minutes | 36.00 seconds |
| 99.5% | 1.84 days | 10.97 hours | 3.65 hours | 50.41 minutes | 7.21 minutes | 18.01 seconds |
| 99.9% | 8.77 hours | 2.20 hours | 43.84 minutes | 10.08 minutes | 1.45 minutes | 3.61 seconds |
| 99.95% | 4.39 hours | 1.10 hours | 21.92 minutes | 5.05 minutes | 43.21 seconds | 1.80 seconds |
| 99.99% | 52.59 minutes | 13.16 minutes | 4.39 minutes | 1.01 minutes | 8.65 seconds | 0.37 seconds |
| 99.999% | 5.27 minutes | 1.32 minutes | 26.31 seconds | 6.05 seconds | 0.87 seconds | 0.05 seconds |
Need Real Monitoring, Not Just Math?
Dotcom-Monitor helps SREs and DevOps teams turn uptime goals into reality.
Get real-time synthetic monitoring, SLA tracking, and global performance insight—all in one platform.
FAQ: SLA & Availability for SREs
1) Are 99.9%+ uptime targets realistic in production environments?
They can be—but only with the right visibility. Many SLAs overlook partial outages, regional latency, or third-party dependencies that impact user experience without triggering traditional monitoring. Dotcom-Monitor uses global, external checks to capture those gaps, giving you a more accurate and defensible uptime number.
2) What should I actually monitor to track an SLA?
SLAs tied to raw uptime miss the point. Monitor externally visible indicators: HTTP success, full page load time, DNS resolution, third-party dependency health. Dotcom-Monitor tracks all of that from outside the firewall, like a real user would.
3) How do I align our internal SLOs with customer-facing SLAs?
Start by measuring SLIs that reflect user experience—not just infra health. Then back into SLOs your team can support. SLAs can promise less than your SLOs—but not the other way around. Tools that provide both internal and external views help bridge the gap.
4) Is there any point in going beyond 99.9% uptime?
This depends on your industry and uptime requirements. If you’re in fintech, healthcare, or anything transactional, Dotcom-Monitor helps validate ultra-high availability claims with third-party verification and alerting.
5) Why not just rely on cloud provider SLAs?
Because “three nines” from AWS doesn’t guarantee your app meets that. SLAs at the infra level don’t reflect your full stack—app bugs, CDN hiccups, or DNS misconfig can kill availability. You need external checks to hold the entire system accountable.
