Service level agreements are quoted in percentages that sound reassuring until you convert them into time. The difference between 99.9% and 99.99% uptime looks like a rounding error, but it is the difference between about nine hours of yearly downtime and about one hour. Each additional nine divides the allowed outage by ten, and the price of the service usually multiplies in the other direction. This tool converts any SLA percentage into allowed downtime per day, week, month, and year using the standard 30-day month and 365-day year conventions, so you can judge whether a vendor promise actually matches your tolerance, negotiate credits from a position of arithmetic certainty, and set monitoring alerts that fire before the budget is spent.
Quick Answer: Enter 99.9% and the tool returns about 43.2 minutes of allowed downtime per month.
Free Online Tool
SLA Uptime Calculator
Turn an SLA percentage into allowed downtime per day, week, month, and year — the numbers behind “five nines”.
Month uses 30 days and year uses 365 days, the standard SLA conventions.
How to Use the SLA Uptime Calculator
- Enter your input in the tool above — for example, 99.9%.
- Choose any options the tool offers, such as the conversion direction or the settings that fit your case.
- Click the main button to run the tool and read the result it displays.
- Check the result against what you expected, then adjust the input and run it again if needed.
- Copy the output into your own document, code, or configuration wherever you need it.
Worked Example
Try it with 99.9%: the tool returns about 43.2 minutes of allowed downtime per month. That example is a good first test whenever you use the tool, because it confirms you entered the input in the expected format before you trust it with your real values. This tool is built for judging vendor SLAs, setting error budgets, and planning monitoring alerts, and the worked example shows the shape of a correct result so you can recognize a wrong one at a glance.
Key Features
- Runs entirely in your browser — nothing you type is uploaded anywhere.
- Built for judging vendor SLAs, setting error budgets, and planning monitoring alerts, with the result shown immediately and in full.
- No account, no sign-up, and no software to install.
- Clear error messages when an input is incomplete or in the wrong format.
- Free to use as often as you like, for study, work, or checking homework.
Best Practices and Tips
- Start with the worked example in the guide, then substitute your own values.
- Double-check units and formats before trusting a result — most tool errors are input errors.
- Keep a note of the exact inputs that produced a result you rely on, so you can reproduce it.
- For anything important, cross-check with a second method or a known test value.
- Bookmark the tool if you use it regularly, so the same workflow is always one click away.
Common Mistakes to Avoid
- Comparing SLAs measured over different periods, which changes the downtime budget.
- Assuming 100% is achievable: every real system has maintenance and failure modes.
- Copying a result without checking it against a known example first.
- Assuming the tool knows your context — it only sees the values you enter.
When This Tool Helps — and When It Doesn’t
This tool helps most when you need a fast, checkable answer for judging vendor SLAs, setting error budgets, and planning monitoring alerts and you can verify the result against a known example. It does not replace professional judgment: for decisions with real consequences, treat the output as one input among several, verify it independently, and remember that the tool can only work with exactly what you enter. Used that way — quick check, verified result, human decision — it saves time without creating false confidence.
Frequently Asked Questions
What does “five nines” (99.999%) allow per year?
About five minutes and fifteen seconds of total downtime per year. That is why five-nines systems need redundancy everywhere: a single unplanned outage of any length can consume the whole budget.
Is downtime measured per month or per year?
It depends on the contract. Some SLAs reset monthly, so a bad month cannot be averaged away by eleven good ones, while others are annual. Always check the measurement window before comparing percentages.
Does scheduled maintenance count against the SLA?
Usually not, if it is announced in the agreed window — but only if the contract says so. Read the exclusions: maintenance, force majeure, and customer-caused outages are commonly carved out.