Uptime/Downtime Calculator
Calculate service uptime and downtime based on SLA percentages.
Frequently Asked Questions
What is an uptime/downtime calculator?
It converts SLA percentage targets (like 99.9%) into actual downtime allowances per day, month, or year, helping you understand what uptime guarantees really mean in practice.
How do I use the calculator?
Enter your desired uptime percentage and select a time period. The tool calculates the maximum allowable downtime and translates the percentage into "nines" of availability.
What does "three nines" or "five nines" mean?
Three nines (99.9%) allows about 8.76 hours of downtime per year. Four nines (99.99%) allows about 52.6 minutes per year. Five nines (99.999%) allows only about 5.26 minutes per year.
How do SLA percentages translate to real downtime?
A 99.9% SLA allows ~43.8 minutes of downtime per month, while 99.99% allows ~4.38 minutes per month. The tool calculates these values for any time period you choose.
Is this tool free?
Yes, ToolDock's uptime/downtime calculator is completely free, requires no signup, and runs entirely in your browser.