Every hosting company has a number on their website: 99.9% uptime guaranteed. It sits next to words like “enterprise” and “reliable” and sounds reassuring. But what does it actually promise — and how much time is your website allowed to be offline?
Let’s turn the marketing number into minutes, then look at what it doesn’t promise, and finish with the questions worth asking any host before you commit.
What 99.9% means in real time
Uptime is measured over a month. The percentage is the share of that month your site responds normally. Here’s the honest maths:
| Uptime | Downtime per month | Downtime per year |
|---|---|---|
| 99% | about 7.3 hours | about 3.7 days |
| 99.9% (“three nines”) | about 43 minutes | about 8.8 hours |
| 99.99% (“four nines”) | about 4.4 minutes | about 53 minutes |
| 99.999% (“five nines”) | about 26 seconds | about 5.3 minutes |
Two things jump out. First: 99% sounds great but means your shop can be dark for a whole working day every month. Second: each extra “nine” is roughly ten times harder to deliver — that’s why five-nines infrastructure costs multiples more. For a small or growing website, 99.9% is the sensible standard: under an hour of downtime a month, most of it in maintenance windows you’ll never notice.
What the uptime promise doesn’t cover
This is the part the sales page won’t highlight. A typical SLA (service level agreement) excludes:
- Planned maintenance. Scheduled updates and reboots usually don’t count against the guarantee — good hosts schedule them at night and announce them in advance.
- Your own issues. An expired domain, a broken plugin that crashes WordPress, or an overdue bill are all downtime — but not the host’s downtime.
- Problems “beyond their control” — upstream network failures, DDoS floods, power cuts. The definition of “beyond control” varies; read it before you need it.
- Compensation limits. The usual remedy is a credit on next month’s bill — often capped, and only if you noticed the downtime and claimed it. No host writes you a cheque for lost sales.
So treat the guarantee as a sign of intent, not insurance. A host confident enough to promise 99.9% and back it with automatic credits is telling you they run serious infrastructure. The refund itself rarely covers what an hour of downtime costs a busy shop.
How to actually check a host’s uptime
- Measure it yourself. Free monitors (UptimeRobot, Better Uptime, StatusCake) ping your site every few minutes and keep a public history. Ten minutes of setup gives you your own truth — this beats any marketing claim.
- Watch response time, not just up/down. A site that answers in 8 seconds is “up” to a monitor but dead to a visitor. Decent hosts keep responses under about a second.
- Ask about the history. A host that publishes a public status page with past incidents has nothing to hide. A host that won’t tell you last quarter’s uptime is telling you something too.
What to ask a host before you sign up
- “What does the SLA exclude?” — you want a specific answer, not a shrug.
- “Is compensation automatic or do I have to claim?” — automatic credits signal confidence.
- “How are maintenance windows announced?” — email a few days ahead is the professional standard.
- “What happens if the whole server fails?” — good answers mention daily backups, spare hardware, and a restore plan measured in hours, not days.
The one-minute summary
- 99.9% = about 43 minutes of possible downtime a month — that’s the normal, sensible standard.
- Every extra nine is 10× harder and much more expensive; don’t pay for nines you don’t need.
- Exclusions (maintenance, your own site’s bugs, compensation caps) matter as much as the headline number.
- Set up your own free monitor — your data beats anyone’s promise.
At AriHosting we run a 99.9% uptime commitment backed by real infrastructure — and daily backups on every plan, so even the rare bad hour never becomes a bad week. See the plans and what’s included.