Uptime / SLA calculator.
Convert any uptime percentage into the downtime it allows — per day, week, month, quarter, and year. Based on a 365-day year and 30-day month.
| Period | Allowed downtime |
|---|---|
| Per day | 1m 26s |
| Per week | 10m 5s |
| Per month | 43m 12s |
| Per quarter | 2h 9m 36s |
| Per year | 8h 45m 36s |
Detection matters as much as the budget. With 5-minute monitoring you can burn minutes of this allowance before you even detect an outage. PingInsight's true 1-second checks catch it almost immediately.
Downtime allowed per year
| Uptime | Name | Downtime / year |
|---|---|---|
| 90% | One nine | 36d 12h |
| 95% | — | 18d 6h |
| 99% | Two nines | 3d 15h 36m |
| 99.5% | — | 1d 19h 48m |
| 99.9% | Three nines | 8h 45m 36s |
| 99.95% | — | 4h 22m 48s |
| 99.99% | Four nines | 52m 34s |
| 99.999% | Five nines | 5m 15s |
| 99.9999% | Six nines | 32s |
Allowed downtime is only half the story — what matters is how fast you detect it. See the downtime cost calculator or learn about 1-second monitoring.
The methodology
Uptime is the share of a period a service is available, so the allowed downtime is simply the rest of the period:
downtime = period_seconds × (1 − uptime% ÷ 100)To keep the numbers comparable to real SLA contracts, the calculator uses fixed period lengths: a 24-hour day, a 7-day week, a 30-day month, a 90-day quarter, and a 365-day year. Real calendar months and leap years vary slightly, but these round conventions make every tier easy to compare.
Worked example: 99.9% over a year
A 365-day year is 31,536,000 seconds. 99.9% uptime leaves 0.1% as downtime, so 31,536,000 × 0.001 = 31,536 seconds — about 8 hours 45 minutes per year, or roughly 43 minutes per month. Add a nine and the budget drops about tenfold: 99.99% allows only ~52 minutes a year.
Frequently asked questions
- How is allowed downtime calculated from an uptime percentage?
- Allowed downtime = period length × (1 − uptime ÷ 100). For 99.9% over a 365-day year that is 31,536,000 seconds × 0.001 = 31,536 seconds, or about 8 hours 45 minutes. The same formula applies to any period — just swap in the number of seconds.
- What year and month length does this calculator use?
- A 365-day (31,536,000-second) year and a 30-day (2,592,000-second) month, with a 24-hour day, 7-day week, and 90-day quarter. Leap years and 28-to-31-day months shift the figures slightly; we use these round conventions so the numbers are easy to compare against an SLA contract.
- Does an SLA percentage guarantee my uptime?
- No. An SLA is a target plus a remedy — usually a service credit — if the target is missed. It does not prevent outages. Whether you actually hit the number depends on your architecture and on how fast you detect and recover, which is why detection speed matters as much as the percentage.
- How do I actually monitor to my SLA?
- Check often enough that a breach cannot hide between checks, confirm failures from multiple locations to avoid false alarms, and alert immediately. PingInsight checks as often as every second from three regions and confirms outages with multi-location quorum.