Cloud uptime explained: what the percentages mean in hours
Availability figures sound alike but differ a lot in practice. This guide turns each percentage into hours and minutes of downtime, and explains what a service agreement does and does not promise.
The arithmetic
A year has 8,760 hours. Each percentage below allows a fixed amount of downtime in that year, and the monthly and weekly figures follow from it. The numbers are approximate, using a 730-hour month and a 168-hour week.
- 99%: about 88 hours a year, about 7 hours a month, about 1 hour 40 minutes a week
- 99.9%: about 8 hours 46 minutes a year, about 44 minutes a month, about 10 minutes a week
- 99.99%: about 53 minutes a year, about 4 minutes a month, about 1 minute a week
- 99.999%: about 5 minutes a year, about 26 seconds a month, about 6 seconds a week
What the number does not cover
- Planned maintenance, if the agreement excludes it. Check how the provider defines a planned window.
- Outages caused by your own code, configuration or changes.
- Problems with your internet connection or your devices.
- Lost or damaged data. Availability is not backup: a system can be up all the time and still hold wrong data.
Two numbers that matter more
The headline percentage tells you little about recovery. Two other figures do. The recovery time objective (RTO) is how long you can be down before the business is hurt. The recovery point objective (RPO) is how much data you can afford to lose, measured as time. Write both down, then ask your provider to show how it meets them.
Questions for any provider
- Which services and regions does the availability commitment cover?
- How are downtime credits calculated, and how do you claim them?
- When was the last restore test of a backup, and what did it prove?
- How are incidents communicated, how quickly, and through which channel?
- Is there a public status page or an alert you can subscribe to?
Where BYTE fits
BYTE is built on Google Cloud, with 99.999% availability. The figure is a starting point, not a promise about every day of use. Ask us what it covers in practice: which services and regions, how backups and recovery are handled, and how incidents are communicated.
BYTE is coming soon. Ask for its current status and its service terms before you decide.
Questions people ask
Is 99.9% enough for a restaurant or a shop?
Often yes, for systems that keep working through short outages. Check what happens to sales during an outage. A POS that cannot take orders for almost nine hours a year is a bigger risk than a reporting tool that is down for the same time.
Does high availability mean my data is safe?
No. A system can be up all the time and still lose or corrupt data. Availability and backup answer different questions.
How do I check an availability claim?
Read the service agreement for the exact service, the measurement period and the exclusions. Ask for the incident history, not only the headline figure.
This guide is general information. Service terms differ between providers, so read the agreement you will sign. Talk to us for a written answer to any question here.