Free tool
Uptime / SLA calculator
See how much downtime an uptime target actually allows — per day, week, month, and year.
| Period | Allowed downtime |
|---|
Hit your SLA — automatically
Spectra confirms outages from multiple regions and alerts you before your error budget runs out. Free forever, no credit card.
Frequently Asked Questions
Answers to common questions teams ask us
What does 99.9% uptime mean?
99.9% uptime ("three nines") allows about 43 minutes of downtime per 30-day month, or roughly 8 hours 45 minutes per year. Use the calculator above to see the exact allowance for any target.
How is allowed downtime calculated?
Allowed downtime = (1 − uptime%) × length of the period. For example, at 99.9% over a 30-day month: 0.001 × 43,200 minutes ≈ 43 minutes.
What's the difference between three, four, and five nines?
99.9% (three nines) ≈ 43 min/month, 99.99% (four nines) ≈ 4.3 min/month, and 99.999% (five nines) ≈ 26 seconds/month. Each extra nine cuts allowed downtime roughly tenfold.
