Free Calculator

SLA Uptime Calculator

Calculate SLA uptime percentages and allowed downtime

Converge Converge Team
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SLA Target

Allowed Downtime

Per Day
1m 26s
Per Week
10m 5s
Per Month
43m 50s
Per Year
8h 46m
Nines
Three Nines (99.9%)

An SLA uptime calculator converts abstract percentages into concrete downtime allowances. When someone says "99.9% uptime," it sounds almost perfect — but it actually allows 8 hours and 46 minutes of downtime per year. Understanding what SLA numbers mean in real minutes is essential for both providers and customers.

According to Gartner, the average cost of IT downtime is $5,600 per minute, or over $300,000 per hour. For e-commerce businesses, Statista estimates that a single hour of downtime during peak shopping costs an average of $500,000 in lost revenue. These numbers explain why the difference between "three nines" and "four nines" matters.

The concept of "nines" in availability is standard across the technology industry. AWS, Azure, and Google Cloud all publish SLAs in this format. AWS guarantees 99.99% for most services, which means no more than 52.6 minutes of downtime per year. Violating that threshold triggers service credits.

For customer support platforms, SLA also extends to response time guarantees. A 1-hour first response SLA means every ticket must receive a human reply within 60 minutes during the defined service window. This calculator focuses on uptime SLAs, but the same mathematical principles apply to any time-based commitment.

How to Use This Calculator

  1. Enter your SLA percentage: Type or use the preset buttons for common SLA tiers (99%, 99.9%, 99.99%, 99.999%).
  2. Read the downtime allowances: See the maximum allowed downtime per day, week, month, and year.
  3. Compare tiers: Try different percentages to understand the real-world difference between SLA levels.

Pro Tips

  • Each nine is 10x harder: Going from 99.9% to 99.99% doesn't just reduce downtime by 0.09% — it reduces it by a factor of 10. The engineering effort and cost increase dramatically with each nine.
  • Exclude planned maintenance: Most SLAs exclude scheduled maintenance windows. Clarify this in your agreements to avoid disputes.
  • Measure from the customer's perspective: Internal monitoring might show 100% uptime, but if customers experience DNS issues or CDN problems, their experience is different.
  • Set realistic targets: A 99.999% SLA requires redundant everything — servers, networks, data centers. For most businesses, 99.9% with good incident response is more practical and cost-effective.

Frequently Asked Questions

What is an SLA?
A Service Level Agreement (SLA) is a contract between a service provider and customer that defines the expected level of service, including uptime guarantees, response times, and remedies for failures. In technology, SLAs typically specify an uptime percentage like 99.9% or 99.99%, which determines the maximum allowed downtime.
What is the difference between 99.9% and 99.99% uptime?
99.9% uptime allows 8 hours and 46 minutes of downtime per year. 99.99% allows only 52 minutes and 36 seconds per year — roughly 10x less. Each additional nine dramatically reduces the allowed downtime window, which is why 'five nines' (99.999%) is considered the gold standard for critical infrastructure.
How do you calculate SLA uptime?
SLA Uptime % = ((Total Time - Downtime) / Total Time) × 100. For example, if a service was down for 4 hours in a 30-day month: ((720 - 4) / 720) × 100 = 99.44%. You can also work backwards: Allowed Downtime = Total Time × (1 - SLA% / 100).
What is a reasonable SLA for a SaaS product?
Most SaaS products offer 99.9% uptime (about 8.7 hours downtime per year). Enterprise services often guarantee 99.95% or 99.99%. Anything below 99.5% is considered poor for paid services. Cloud providers like AWS and Azure typically offer 99.99% for their core services.
What happens when an SLA is breached?
Most SLAs include service credits as compensation for breaches. Typically, providers offer 10-25% credit on the monthly bill per defined violation threshold. Some enterprise contracts include financial penalties or termination rights. The key is having clear, measurable metrics and an agreed process for claiming credits.
Should SLA be measured in calendar time or business hours?
It depends on the service. Customer-facing applications should use calendar time (24/7) since customers expect availability anytime. Internal tools may use business hours (e.g., 8am-6pm weekdays). Make sure the SLA clearly defines the measurement period to avoid disputes.

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