99.9% Uptime SLA Calculator
Calculate maximum allowed downtime for any SLA percentage. Convert uptime commitments to real-world downtime allowances for daily, weekly, monthly, quarterly, and yearly periods.
Enter SLA Percentage
Enter an uptime SLA percentage (e.g., 99.9) to calculate maximum allowed downtime for your service level agreement
Maximum Allowed Downtime for 99.9% SLA
Based on 24/7/365 continuous operation (Three Nines)
Understanding 99.9% Uptime (Three Nines)
Three nines (99.9%) uptime is the industry standard for most commercial web applications and SaaS products. It provides a good balance between reliability and operational complexity.
With a 99.9% uptime SLA, your service can be unavailable for a maximum of 8 hours, 45 minutes and 36 seconds per year while still meeting your uptime commitment. This translates to approximately 43 minutes and 12 seconds per month.
Typical Use Cases
- -Business web applications
- -Content management systems
- -Customer support platforms
- -Marketing automation tools
- -Project management software
Infrastructure Requirements
- -Load balancing
- -Database replication
- -Automated deployments
- -Application monitoring
- -Incident management process
Key Challenges
With approximately 8 hours and 45 minutes of allowed downtime per year, three nines is achievable with good engineering practices but still requires attention to reliability.
SLA Uptime Levels Comparison
Common uptime percentages and their allowed yearly downtime
How to Calculate Uptime SLA
The formula and methodology behind SLA calculations
These calculations assume continuous 24/7/365 operation. A year has 31,536,000 seconds, which serves as the base for all yearly calculations.
Monthly calculations use 30 days (2,592,000 seconds), which is an industry standard approximation.
Frequently Asked Questions About Uptime SLA
Common questions about service level agreements and uptime calculations
What is an SLA (Service Level Agreement)?
An SLA is a commitment between a service provider and a customer that defines the expected level of service, including uptime guarantees, response times, and remedies for failing to meet those commitments. The uptime percentage is one of the most important SLA metrics.
How is uptime percentage calculated?
Uptime percentage is calculated using the formula: ((Total Time - Downtime) / Total Time) × 100. For example, if a service was down for 8 hours in a year (8,760 hours), the uptime would be ((8760 - 8) / 8760) × 100 = 99.91%.
What does "nines" mean in uptime?
The term "nines" refers to the number of 9s in the uptime percentage. Two nines means 99%, three nines means 99.9%, four nines means 99.99%, and five nines means 99.999%. Each additional nine represents a 10x improvement in reliability.
Why is the cost of achieving higher uptime exponential?
Each additional nine of uptime requires increasingly sophisticated infrastructure, redundancy, and operational practices. Going from 99% to 99.9% might require load balancing, while going from 99.99% to 99.999% might require multiple data centers with real-time replication.
Does SLA downtime include scheduled maintenance?
This depends on the specific SLA agreement. Some SLAs exclude scheduled maintenance windows from downtime calculations, while others include all downtime regardless of the cause. Always read the fine print in your service agreements.
How do I monitor my actual uptime?
Use an uptime monitoring service like SiteBot to continuously check your services from multiple locations. These tools track response times, detect outages, and calculate your actual uptime percentage over time.
Industry SLA Standards by Sector
Typical uptime requirements across different industries and service types
Enterprise Cloud Services
- AWS EC2: 99.99%
- Google Cloud Compute: 99.99%
- Microsoft Azure VMs: 99.99%
- Cloudflare: 100% (network)
SaaS Applications
- Salesforce: 99.9%
- Slack: 99.99%
- GitHub: 99.9%
- Zoom: 99.9%
Critical Infrastructure
- Payment processors: 99.999%
- Telecom networks: 99.999%
- Banking systems: 99.99%+
- Healthcare systems: 99.99%+
Track Your Actual Uptime Performance
Setting an SLA is just the beginning. Monitor your services 24/7 with SiteBot to measure actual uptime, detect outages instantly, and prove compliance with your SLA commitments.