Uptime Calculator determines how much downtime a website experiences over a given period, revealing the percentage of time it remains online. By inputting the total minutes, hours, or days of downtime, you get the fraction or percent of availability. Many hosting providers advertise 99.9% uptime, but even a small outage can add up. The tool helps you track real performance against service-level agreements. By diagnosing repeated outages, you can press your hosting provider for solutions or consider an upgrade. High uptime is key for user trust, so consistent tracking ensures your site meets your availability goals.