What does 99.9% uptime actually mean?
More downtime than you think. 99.9% still allows nearly 9 hours offline every year, and your SLA probably measures it monthly, which hides even more. Convert any uptime percentage into real hours and minutes, or turn your own outage history into an honest uptime figure.
Enter an uptime percentage
Type any figure from an SLA, a carrier contract, or a vendor datasheet.
Enter your actual downtime
Add up your outages from tickets, monitoring, or memory. Be honest, count the ones nobody logged.
The nines, side by side
Each extra nine cuts downtime by a factor of ten, and typically multiplies the cost of achieving it. The row matching your figure is highlighted.
| Uptime | Per day | Per week | Per month | Per year |
|---|
How this converter works
Simple arithmetic, stated plainly so you can defend any figure you quote from this page.
- Downtime = (100% minus the uptime percentage) multiplied by the length of the period.
- Periods used: a day is 24 hours, a week is 7 days, a month is 30.44 days (a year divided by 12), and a year is 365.25 days. Some SLAs define a month as exactly 30 days; the difference is small but check your contract's wording.
- Working days lost assumes an 8-hour working day. Adjust mentally if your sites trade longer.
- What a percentage hides: availability figures say nothing about when the downtime lands. Nine hours spread across a year in overnight maintenance windows is invisible. The same nine hours during peak trading is a crisis. Averages do not feel outages; people do.
Figures are estimates provided for guidance only. Check the definitions in your own SLA.
You now know the hours. The next question is the money. Our downtime cost calculator turns hours offline into lost revenue, idle staff cost, and recovery time across your whole estate.
Calculate the costThe gap between the nines is where businesses bleed
A single connection, however good the carrier, tends to deliver two or three nines in practice. Moving to four or five is not about buying a better line. It is about having a second, independent path with automatic failover, so one provider's bad day never becomes yours.
We design and supply resilient connectivity for multi-site businesses. If your SLA promises three nines and your sites are living at two, tell us about your estate and our engineering team will spec what closing that gap would take.