SLA Uptime Calculator

Convert SLA uptime percentages into allowed downtime per year, month, week, and day. Plan service level agreements for ISPs, hosting providers, and enterprise infrastructure with realistic availability targets.
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Allowed Downtime
Per Day
1m 26s
86.4 seconds
Per Week
10m 5s
604.8 seconds
Per Month
43m 48s
2628.0 seconds
Per Year
8h 45m 36s
31536.0 seconds
Availability Assessment
SLANinesPer DayPer MonthPer Year
99.999%51s26s5m 15s
99.99%49s4m 23s52m 34s
99.95%3.343s21m 54s4h 22m 48s
99.9%31m 26s43m 48s8h 45m 36s
99.5%2.37m 12s3h 39m1d 19h 48m
99%214m 24s7h 18m3d 15h 36m
High Availability99.9% availability is 3 nines
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Overview

The SLA Uptime Calculator converts a service level agreement uptime percentage into the maximum allowed downtime per day, week, month, and year. It helps ISPs, hosting providers, managed service providers, and enterprise teams set realistic availability targets and understand what a promised percentage actually means in real time.

Common Use Cases

How to Use

1
Enter the uptime percentage promised in the service level agreement, such as 99.9 or 99.99.
2
Use the quick tier buttons to select a common availability target.
3
Review the allowed downtime per day, week, month, and year.
4
Compare the selected target against common SLA tiers in the reference table.

Example Scenario

99.9% Uptime ISP

An ISP promises 99.9% availability on a residential fiber plan. This allows roughly 8.76 hours of downtime per year, or about 43.8 minutes per month, before the provider breaks its SLA commitment.

Technical Notes

Downtime is calculated as the time unavailable during the measurement period. For 99.9% uptime, downtime is 0.1% of the year, or about 8.76 hours.

The number of nines indicates the availability class. 99% is two nines, 99.9% is three nines, 99.99% is four nines, and 99.999% is five nines.

Calculations use 365 days per year. Monthly downtime is one twelfth of the yearly downtime.

SLA uptime may or may not exclude scheduled maintenance windows depending on the specific contract terms.

Reaching four or five nines usually requires redundant power, network, and hardware with automatic failover rather than a single component design.

Common Mistakes

Frequently Asked Questions

99.9% uptime allows about 8.76 hours of downtime per year, about 43.8 minutes per month, and about 1.44 minutes per day.

99.99% allows about 52.6 minutes of downtime per year, roughly ten times less than the 8.76 hours allowed by 99.9%.

Many SLAs exclude scheduled maintenance windows, but the exact terms must be defined in the contract to avoid disputes.

The number of nines is a shorthand for the availability class. Each additional nine reduces the allowed downtime by roughly a factor of ten.

Higher availability requires more expensive redundancy and engineering. Choose a target that matches the business criticality of the service.

Related Topics

Service level agreementUptime monitoringAvailability tiersNetwork reliabilityFault toleranceRedundant infrastructureMaintenance windowsISP service qualityHosting reliabilitySLA credits