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Uptime Simulators

Interactive SLA calculator and the complete guide to the 9 nines of availability. Understand how much downtime each reliability level actually allows — from 90% (one nine) to 99.9999999% (nine nines).

SLA Uptime Calculator
Enter any SLA percentage (e.g., 99.9, 99.99, 99.999) to see allowed downtime across different time periods.
%

Quick Select:

Daily
1m 26.400s
0.1000% of period
Weekly
10m 4.800s
0.1000% of period
Monthly (30d)
43m 11.1000s
0.1000% of period
Quarterly (90d)
2h 9m 35.1000s
0.1000% of period
Yearly (365d)
8h 45m 35.1000s
0.1000% of period

Closest match: Three Nines (99.9% uptime) — exact match!

Understanding SLA Uptime Percentages

What are “nines” in uptime? The term “nines” refers to the number of consecutive 9s in a service's uptime percentage. One nine (90%) allows 36.5 days of downtime per year, while five nines (99.999%) allows only ~5.26 minutes. Each additional nine represents a 10× improvement in reliability.

How is uptime calculated? Uptime percentage = (Total Time − Downtime) ÷ Total Time × 100. For a 365-day year (31,536,000 seconds), 99.9% uptime means 31,536,000 × 0.001 = 31,536 seconds (8.76 hours) of allowed downtime.

Why does each nine matter? The difference between 99.9% and 99.99% sounds small (0.09%) but represents a reduction from 8.76 hours to 52.6 minutes of annual downtime — a 10× improvement that typically requires significant infrastructure investment in redundancy, monitoring, and operational excellence.

Common SLA tiers: Most SaaS products target 99.9% (three nines) as their baseline SLA. Enterprise customers often require 99.99% (four nines). Mission-critical systems like DNS providers and payment networks target 99.999% (five nines). Beyond six nines, the reliability levels become largely theoretical for general-purpose distributed systems.