SLA Uptime Calculator
Enter an SLA percentage to see exactly how much downtime it allows per year, month, week and day — useful for reviewing hosting, cloud, and vendor SLA contracts.
Source: standard uptime/downtime math (the industry-standard "nines" convention used in hosting and cloud SLAs). See the full methodology page. Reviewed: July 2026.
Uptime, downtime, SLA, or availability calculator?
These describe the same relationship viewed from different angles. Uptime and downtime are complements of each other (downtime % = 100% − uptime %); availability is the general engineering term for the same percentage; SLA is the contractual document that specifies which uptime percentage a vendor commits to. Enter a percentage above and this tool converts it into concrete downtime across every common time window — covering all four framings in one place.
Why SLA downtime numbers matter
An SLA of "99.9% uptime" sounds close to "always up" — but it permits over 8 hours of downtime a year, which is a very different risk profile than 99.99% (about 52 minutes/year) or 99.999%, the so-called "five nines" (about 5 minutes/year). This calculator converts any percentage directly into time, so you can compare vendor SLAs on equal footing.
Common SLA tiers
99% ≈ 3.65 days/year downtime, 99.9% ≈ 8.76 hours/year, 99.95% ≈ 4.38 hours/year, 99.99% ≈ 52.6 minutes/year, 99.999% ≈ 5.26 minutes/year. Most cloud IaaS providers commit to 99.9%–99.99% for compute, and higher for managed/multi-zone services.
Does SLA downtime include planned maintenance?
It depends on the contract — many vendor SLAs explicitly exclude scheduled maintenance windows from the downtime calculation. Always check the SLA's exact definition of "downtime" before relying on this figure contractually.
What SLA credit should I expect if a vendor misses their target?
This varies by provider and is defined in the contract itself (typically a percentage of monthly fees, tiered by how far below target the actual uptime fell). This calculator only computes time, not compensation.