Calculate hosting
downtime by SLA.
Use the HostingGrader Uptime SLA Calculator to see how much downtime different uptime guarantees may allow per day, month, and year before choosing a hosting provider.
What does 99.9% really mean?
A hosting SLA can sound strong, but even small percentage differences can mean real downtime over a full year.
Uptime SLA Calculator
Enter an uptime percentage to estimate how much downtime may be allowed over a day, month, and year.
Why uptime SLA matters
An uptime guarantee helps explain how much availability a host promises, but the real value depends on downtime limits, support response, and the provider’s terms.
Small percentages matter
The difference between 99.9% and 99.99% can mean hours of downtime over a year. That can matter for stores, business sites, and high-traffic projects.
SLA credits vary
Some hosts offer credits when uptime falls below the promise, but credits may be limited and may not fully cover lost traffic, leads, or sales.
Maintenance may be excluded
Planned maintenance, third-party issues, user-side problems, or certain outages may be excluded from the provider’s SLA calculation.
Common uptime SLA examples
These examples show why it helps to calculate downtime before assuming a hosting guarantee is enough.
99% uptime
Allows roughly 3.65 days of downtime per year. This may be too much for serious business websites or ecommerce stores.
99.9% uptime
Allows roughly 8 hours and 46 minutes of downtime per year. It is common, but still worth comparing against stronger options.
99.99% uptime
Allows roughly 52 minutes of downtime per year. This is stronger, but the actual SLA terms still matter.