You always hear 98% this, 99% that, but what do the numbers really mean? Let’s start with a mathematical look at these server uptime numbers:

98% uptime = 28.8 minutes / day –> 3.4 hours / week –> 14.4 hours / month –> 7.3 days / year
99% uptime = 14.4 minutes /day –> 1.7 hours / week –> 7.2 hours / month –> 3.65 days / year
99.5% uptime = 7.2 minutes /day –> 0.84 hours / week –> 3.6 hours / month –> 1.83 days / year
99.9% uptime = 1.44 minutes / day –> 0.17 hours / week –> 0.72 hours / month –> 8.8 hours / year

Suppose your website makes $1000/month from Adsense, affiliate programs, or anything else which is dependant on your website being up (eg. not having advertisers that pay a fixed monthly rate). In such a case, you could expect to lose about $250 per year on a server with 98% uptime that you could otherwise have made on a server with 99.9% uptime. If your website was making $2000/month, the lost sales on a 98% uptime server would be about $500 per year. At $10,000/month, 98% uptime would cost you $2500 per year in lost sales.

This mean that if your website/websites collectively make $1000 per month, you should be willing to pay $20 more per month for 99.9 % uptime over 98% uptime. If you care about user experience, you might value the better uptime higher still. If your websites are making $2000/month, that superior uptime is worth at least $40/month more and at $10,000 per month, it should be worth $200/month more.

Obviously the more your website makes, the more expensive downtime is going to be. It’s not a big deal if this blog goes down — you can always read the story later today or tomorrow. On the other hand, if an online store goes down, people may decide to just buy the product elsewhere — likely from one of your competitors which might also result in you losing repeat business this customer might otherwise have given you in the future.

When looking at server uptime numbers, be sure to find out what exactly a company means by “server uptime”. You’ll find that not all companies have the same definition of what is and what is not considered. Most people only consider a few things when looking for a web host — the cost, the hardware, and sometimes the uptime. I would highly recommend you don’t forget to check out their customer support and read customer reviews before signing up. Low uptime is great, especially if your host’s definition of uptime is what you consider it to mean, but of what use is high uptime if there’s nobody to help when your website does go down?

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