Uptime & SLA Calculator (Downtime per Year, Month, Week)
Free calculator: convert an availability percentage like 99.9% into allowed downtime, and calculate the combined SLA of multiple cloud services.
Combined SLA of several services
Services that depend on each other (in series) multiply their availability, so the overall SLA is lower than any single one. Redundant copies (in parallel) raise it.
How the math works
Availability = uptime ÷ total time. At 99.9% ("three nines"), a service can be down about 8.8 hours a year; at 99.99%, about 53 minutes. For dependent services, multiply availabilities: 99.9% × 99.9% = 99.8%. For N redundant copies, availability = 1 − (1 − A)N.
Learn more in Scalability vs. Elasticity vs. High Availability.
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