How to use the Uptime SLA Calculator
- 1. Choose a modeAllowed downtime, uptime from downtime, or combined services.
- 2. Enter the numbersAn SLA percentage, minutes of downtime, or one SLA per line.
- 3. Read the tableSee the allowed downtime for every period.
Worked example: 99.9%
A 99.9% SLA allows 43.83 minutes of downtime per month. The calculation is 0.1% of a month: a month averages 30.44 days, or 43,830 minutes, and 0.001 × 43,830 = 43.83. The same SLA allows 1.44 minutes a day, 10.08 minutes a week and 8.77 hours a year. Each extra nine cuts downtime by ten: 99.99% allows about 4.38 minutes a month, and 99.999% about 26 seconds.
Change the mode to Uptime % from downtime to grade a real month: 30 minutes of outage in a month is 99.9316% uptime.
Why chains of services are less available
When a request needs several services to all be up, their availabilities multiply. The default chain of 99.99%, 99.95% and 99.9% gives about 99.84%, which allows roughly 70 minutes of downtime a month, more than any single part. That is why adding dependencies quietly lowers reliability, and why critical parts run as redundant copies, where one failing is not an outage.
- Check how your provider measures: monthly or yearly, and whether planned maintenance counts.
- SLA credits usually repay a fraction of the bill, not your lost business.
- Error budgets use the same numbers: 43 minutes a month is the room you have for risky releases.
For transfer times, try the bandwidth and download time calculator; for traffic and error counts, the access log analyzer.
Frequently asked questions
What does five nines mean?
99.999% availability, which allows about 5.26 minutes of downtime per year.
Which month length is used?
An average month of 30.44 days (365.25 ÷ 12). A 31-day month allows slightly more minutes, a 28-day month slightly fewer.
Is the Uptime SLA Calculator free?
Yes, the Uptime SLA Calculator is free. The first time you see your first result, you are asked for your name and WhatsApp number once. After that, this and every other Uncodemy tool opens straight away without the form.