Free tools / Uptime calculator
Uptime calculator
Turn an SLA percentage into downtime per day, week, month, and year, or work backwards from an outage to the uptime you actually delivered.
Uptime target
per month, unless notedType any value, or pick a common tier.
| Period | Allowed downtime |
|---|---|
| Per day | 1m 26s |
| Per week | 10m 5s |
| Per month (30.44 days) | 43m 50s |
| Per quarter | 2h 11m |
| Per year (365.24 days) | 8h 45m |
Downtime you had
Add up every incident in the window, including partial outages if your SLA counts them.
| SLA | Budget | Remaining |
|---|
How the uptime calculation works
Allowed downtime is the period length multiplied by the share of time you are permitted to be down: downtime = period × (1 − uptime ⁄ 100). A 99.9% target over a 30.44-day month is 2,629,746 seconds × 0.001, which is 43 minutes and 50 seconds. Going the other way, achieved uptime is (1 − downtime ⁄ period) × 100.
This calculator uses the average Gregorian month (365.2425 ⁄ 12 = 30.44 days) and year (365.2425 days). Some SLAs define a month as the calendar month that actually elapsed; a 28-day February gives you about 8% less budget than a 31-day month at the same percentage.
Uptime SLA table
| Uptime | Per day | Per week | Per month | Per year |
|---|---|---|---|---|
| 90% one nine | 2h 24m | 16h 48m | 3d 1h 2m | 36d 12h 34m |
| 95% | 1h 12m | 8h 24m | 1d 12h 31m | 18d 6h 17m |
| 99% two nines | 14m 24s | 1h 40m | 7h 18m | 3d 15h 39m |
| 99.5% | 7m 12s | 50m 24s | 3h 39m | 1d 19h 49m |
| 99.9% three nines | 1m 26s | 10m 5s | 43m 50s | 8h 45m |
| 99.95% | 43s | 5m 2s | 21m 55s | 4h 22m |
| 99.99% four nines | 8.6s | 1m | 4m 23s | 52m 36s |
| 99.999% five nines | 0.86s | 6s | 26s | 5m 16s |
What the nines mean in practice
- 99% (two nines) is seven hours a month. Fine for an internal tool nobody uses overnight; not something you would put in a customer contract.
- 99.9% (three nines) is the most common promise for SaaS. Forty-four minutes a month means one bad deploy, caught in ten minutes and rolled back, uses a quarter of the budget.
- 99.95% and 99.99% (four nines) leave 22 and 4.4 minutes a month. At this level a human cannot be in the loop for detection; a check has to page you, and the fix has to be a runbook, not an investigation.
- 99.999% (five nines) is 26 seconds a month. It is a property of redundant architecture, not of monitoring, and almost no single-region service honestly achieves it.
Measuring uptime, not just calculating it
A calculator tells you the budget. A monitor tells you whether you spent it. Two details matter when you pick one:
- Check interval sets your resolution. With a check every 5 minutes, an outage is only ever known to the nearest five minutes, and a 4-minute blip can be missed entirely. For a 99.99% target the whole monthly budget is 4 minutes and 23 seconds, so you need 60-second checks to measure it at all. ScaledPapers runs 5-minute checks on Free and 60-second checks on Pro.
- Confirmation avoids false downtime. A single failed probe from one network should not count as an outage. ScaledPapers only opens an incident after a configurable number of consecutive failures, and only closes it after consecutive successes, so your recorded uptime reflects the service and not a flaky route.
Frequently asked questions
- How much downtime is 99.9% uptime?
- 1 minute 26 seconds per day, 10 minutes 5 seconds per week, 43 minutes 50 seconds per month, and 8 hours 45 minutes per year.
- How much downtime is 99.99% uptime?
- 8.6 seconds per day, about 1 minute per week, 4 minutes 23 seconds per month, and 52 minutes 36 seconds per year.
- Does scheduled maintenance count against uptime?
- It depends on the SLA text. Most vendor SLAs exclude announced maintenance windows; most internal SLOs do not, because users are affected either way. If yours excludes maintenance, subtract the window from the period before you divide.
- Is uptime measured per month or per year?
- Commercial SLAs almost always reset monthly, because credits are issued against monthly invoices. Yearly figures are useful for planning but hide the fact that one 45-minute outage already breaches a 99.9% monthly SLA.
- Can I link to a specific result?
- Yes. The uptime percentage is kept in the URL as
?sla=99.95, so you can paste the link into a ticket or a doc.
Know when you spend the budget
ScaledPapers checks your endpoints every 60 seconds from five regions, confirms failures before opening an incident, and keeps 90 days of history you can point an auditor at. Free for 5 checks at 5-minute intervals, no card.