uptime % ↔ downtime per period
Uptime / Downtime Calculator
Enter an uptime percentage and see the maximum downtime it allows per day, week, month and year, or go the other way and turn real downtime into the uptime percentage you achieved.
Uptime percentage
Allowed downtime is (1 − uptime) × period, on a 365.25-day year (so a month is 30.44 days). Most SLAs are measured monthly.
Max downtime at 99.9%
Per day
1m 26s
Per week
10m 5s
Per month
43m 50s
Per quarter
2h 11m
Per year
8h 45m
Had downtime? Get the uptime %
Uptime achieved
99.9019%
meets the 99.9% tier
Uptime levels: downtime per period
Maximum downtime each uptime level allows.
| Uptime | day | week | month | quarter | year |
|---|---|---|---|---|---|
| 90% | 2h 23m | 16h 47m | 3d 1h | 9d 3h | 36d 12h |
| 95% | 1h 12m | 8h 24m | 1d 12h | 4d 13h | 18d 6h |
| 98% | 28m 48s | 3h 21m | 14h 36m | 1d 19h | 7d 7h |
| 99% | 14m 24s | 1h 40m | 7h 18m | 21h 54m | 3d 15h |
| 99.5% | 7m 12s | 50m 24s | 3h 39m | 10h 57m | 1d 19h |
| 99.9% | 1m 26s | 10m 5s | 43m 50s | 2h 11m | 8h 45m |
| 99.95% | 43.2s | 5m 2s | 21m 55s | 1h 5m | 4h 22m |
| 99.99% | 8.6s | 1m | 4m 23s | 13m 9s | 52m 36s |
| 99.999% | 864 ms | 6s | 26.3s | 1m 19s | 5m 16s |
| 99.9999% | 86 ms | 605 ms | 2.6s | 7.9s | 31.6s |
About this tool
This uptime and downtime calculator answers the question every status page raises: if a service promises 99.9% uptime, how much downtime is that? Type a percentage and it shows the maximum outage allowed per day, week, month, quarter and year, so an abstract number like 99.99% turns into a concrete 4.38 minutes a month.
It also works the other way. Enter the downtime you actually had over a period - say 43 minutes last month - and it returns the uptime percentage you achieved and the tier it lands in, which is what you need when you report on an incident or check a provider against its promise.
Everything is computed in your browser and nothing is uploaded. A year is 365.25 days (so a month is 30.44 days), which lines up with the canonical reference figures. For SLA contracts, error budgets and combining several services into one end-to-end number, see the companion SLA & Uptime Calculator linked under Related tools.
How to use it
- 01Type your target uptime percentage, or tap a preset chip (99%, 99.9%, 99.99% and so on).
- 02Read the maximum allowed downtime per day, week, month, quarter and year; the monthly figure is highlighted because most SLAs measure monthly.
- 03To go the other way, enter the real downtime you observed and the period it covered to get the uptime percentage you achieved.
- 04Compare every common uptime level in the reference table, and use copy to drop the summary into a ticket or report.
Frequently asked questions
What does 99.9% uptime mean in downtime?+
99.9% ("three nines") allows about 8.77 hours of downtime per year, 43.83 minutes per month, 10.08 minutes per week or 1.44 minutes per day. Type the percentage and the calculator shows all of these at once.
How much downtime is 99.99% vs 99.999%?+
Each extra nine cuts the budget by roughly ten times. 99.99% ("four nines") allows about 4.38 minutes per month; 99.999% ("five nines") about 26 seconds per month, or roughly 5.26 minutes per year.
How do I calculate the uptime percentage from downtime?+
Uptime % = (period - downtime) / period x 100. Enter the downtime you had and the period it covered in the second panel and the calculator does the math, then tells you which uptime tier it meets.
Is a month 30 days or 30.44 days here?+
This tool uses 30.44 days (one twelfth of a 365.25-day year), which matches the downtime figures most uptime references quote. Some contracts use a flat 30-day month or the actual calendar month, which shifts the monthly number slightly, so check how your SLA defines the window.
Does scheduled maintenance count as downtime?+
It depends on the agreement. Many SLAs exclude announced maintenance windows and only count unplanned outages, so the real budget can be larger than the raw percentage implies. Always read the exclusions in the contract.
How is this different from the SLA calculator?+
This page is the quick uptime-to-downtime converter, and back. The SLA & Uptime Calculator adds SLA-contract features: reversing a downtime budget into the SLA percentage you need, and combining dependent or redundant services into one composite figure.