Uptime & Downtime Calculator
Turn any uptime percentage into real downtime per day, week, month and year — and finally understand what the “nines” in a hosting SLA really mean.
What an uptime percentage really buys you
When a web host, cloud provider or service promises “99.9% uptime” in its service-level agreement (SLA), it sounds almost perfect — but 0.1% of a year is still nearly nine hours of allowed downtime. The famous “nines” shorthand hides how big the gaps between tiers are: each extra nine cuts permitted downtime by roughly a factor of ten. This calculator turns any percentage into plain, real-world downtime per day, week, month and year.
Use it to sanity-check a hosting promise, set a realistic target for your own service, or understand what an outage means against your SLA. The difference between three nines and four nines is the difference between a long lunch of downtime each month and just a few minutes.
The nines, at a glance
| Uptime | Per day | Per month | Per year |
|---|---|---|---|
| 99% (two nines) | 14.4 min | ~7.3 hr | 3.65 days |
| 99.9% (three nines) | 1.44 min | ~43.8 min | 8.77 hr |
| 99.99% (four nines) | 8.6 s | ~4.38 min | 52.6 min |
| 99.999% (five nines) | 0.86 s | ~26.3 s | 5.26 min |
Reading a hosting SLA. Check whether the percentage is measured monthly or yearly, what counts as “downtime” (planned maintenance is often excluded), and what compensation you actually get — usually a small service credit, not a refund of lost business. A higher number is only worth paying for if your service genuinely needs it.
Frequently asked questions
How much downtime does 99.9% uptime allow?
About 8 hours and 46 minutes per year, or roughly 43 minutes per month. It sounds tiny, but 0.1% of a year is still significant — which is why high-availability services aim for 99.99% or more.
What do 'three nines' and 'five nines' mean?
They are shorthand for uptime percentages: three nines is 99.9%, four nines 99.99%, five nines 99.999%. Each additional nine cuts the allowed downtime by roughly ten times, and typically costs much more to achieve.
Is 100% uptime possible?
In practice, no. Hardware fails, software needs updates and networks have hiccups. Serious providers target 99.9% to 99.999% and design redundancy to get close, but no honest SLA promises a literal 100%.
Does planned maintenance count as downtime?
It depends on the SLA. Many providers exclude scheduled maintenance windows from their uptime calculation, so the real availability you experience can be lower than the headline figure. Always read the definitions in the agreement.
How do I choose the right uptime target?
Match it to the cost of being offline. A personal blog is fine at 99%; an online shop losing sales every minute may justify 99.99%. Each extra nine adds cost and complexity, so buy only the availability you genuinely need.
This tool runs entirely in your browser — nothing you type is sent to our servers. Tudug is reader-supported and may earn from ads.
More free tools
Password Generator
Create strong, random passwords with custom length and character sets.
Open tool →Download Time Calculator
Estimate download time from file size and connection speed.
Open tool →Screen Resolution & DPI
Work out pixel density, aspect ratio and total megapixels.
Open tool →