Uptime & SLA Downtime Calculator

Calculate exactly how much downtime each SLA level allows. Enter an uptime percentage or a downtime budget to see the conversion. Used by DevOps teams, SREs, and IT managers to plan SLA commitments and estimate downtime costs.

Desired Uptime (%)

Allowed downtime per year at 99.9% uptime8h 46m

Per Month44m

Per Week10m

Per Day1m

SLA Comparison Table

SLA Level	Downtime / Year	Downtime / Month	Downtime / Week	Downtime / Day
99%	3d 15h 40m	7h 18m	1h 41m	14m
99.5%	1d 19h 50m	3h 39m	50m	7m
99.9%	8h 46m	44m	10m	1m
99.95%	4h 23m	22m	5m	43s
99.99%	53m	4m	1m	9s
99.999%	5m	26s	6s	1s

What Does 99.9% Uptime Mean?

An uptime SLA (Service Level Agreement) of 99.9% — often called “three nines” — means your service is allowed a maximum of 8 hours and 46 minutes of downtime per year, or roughly 43 minutes per month. This is one of the most common SLA tiers offered by cloud providers, hosting companies, and SaaS platforms.

While 99.9% sounds nearly perfect, the allowed downtime can be significant for mission-critical applications. E-commerce sites, payment processors, and healthcare platforms often require 99.99% or higher to avoid revenue loss and user trust erosion.

Common SLA Uptime Tiers Compared

Different industries and service types require different levels of availability. Here is what each common SLA tier means in practical terms:

SLA Level	Common Name	Downtime / Year	Downtime / Month	Typical Use Case
99%	Two nines	3d 15h 36m	7h 18m	Internal tools, dev environments
99.9%	Three nines	8h 46m	43m 50s	SaaS apps, business websites
99.95%	Three and a half nines	4h 23m	21m 55s	E-commerce, customer portals
99.99%	Four nines	52m 36s	4m 23s	Financial services, healthcare
99.999%	Five nines	5m 16s	26s	Emergency services, critical infrastructure

How Much Does Downtime Cost?

The cost of downtime varies dramatically by industry and company size. According to industry research, the average cost of IT downtime is estimated at $5,600 per minute for large enterprises. For small and mid-sized businesses, even a few hours of downtime can result in thousands of pounds in lost revenue, damaged reputation, and reduced customer trust.

Factors That Affect Downtime Cost

Lost revenue — direct sales lost during outage
Productivity loss — employees unable to work
SLA penalties — contractual credits owed to customers
Recovery costs — engineering time to diagnose and fix
Reputation damage — customer churn and negative reviews
Data loss — potential data corruption during unplanned outages

This is why monitoring your uptime continuously and catching issues early is critical. A proactive monitoring setup can reduce mean time to detect (MTTD) from hours to seconds.

Got questions?

Frequently Asked Questions

Everything you need to know about Uptrue — no fluff.

What is an SLA (Service Level Agreement)?

An SLA is a contract between a service provider and a customer that defines the expected level of service, including uptime guarantees, response times, and remedies (such as service credits) if those targets are not met. SLAs are standard in cloud computing, web hosting, and SaaS.

What is the difference between uptime and availability?

Uptime measures the total time a system is operational, while availability measures the percentage of time a system is accessible and functioning correctly. In practice, these terms are often used interchangeably, but availability also accounts for planned maintenance windows that may not count as downtime in an SLA.

How is uptime percentage calculated?

Uptime percentage is calculated as: (Total time - Downtime) / Total time x 100. For example, if a service was down for 43 minutes in a 30-day month (43,200 minutes), the uptime would be (43,200 - 43) / 43,200 x 100 = 99.9%.

What does "five nines" (99.999%) availability mean?

Five nines availability means a service can only be down for approximately 5 minutes and 16 seconds per year, or about 26 seconds per month. This level of availability is extremely difficult and expensive to achieve, typically requiring redundant infrastructure, automatic failover, and multi-region deployments.

How do I monitor my website uptime?

You can monitor website uptime using a service like Uptrue that checks your website at regular intervals (as frequently as every minute) from multiple locations. When your site goes down, you receive instant alerts via email, Slack, SMS, or webhook so you can respond quickly.

What is MTTR and MTTD?

MTTD (Mean Time to Detect) is the average time it takes to discover a problem. MTTR (Mean Time to Recover) is the average time it takes to restore service after a failure is detected. Reducing both metrics is key to maintaining high uptime percentages.

Does planned maintenance count against SLA uptime?

This depends on the specific SLA agreement. Many providers exclude scheduled maintenance windows from their uptime calculations, provided they give advance notice (typically 24-72 hours). Always check the fine print of your provider's SLA.

What uptime SLA should I offer my customers?

The right SLA depends on your infrastructure, budget, and customer expectations. Most SaaS platforms start with 99.9% and upgrade to 99.95% or 99.99% as they mature. Offering an SLA you cannot consistently meet will erode trust faster than not having one at all.

Monitor your uptime automatically

Stop calculating downtime manually. Uptrue's HTTP uptime monitoring tracks your sites every minute with two-region confirmation and pairs with heartbeat monitoring for cron jobs and background workers — alerting you the moment something goes wrong.

Start Monitoring Free