SLA math
99.99% uptime: four nines in plain time
Under an hour of downtime per year. Easy to put on a sales slide; hard to keep once humans deploy weekly.
Target
99.99%
Allowed downtime / year
53 minutes / year
Per month (avg)
4.4 minutes
Who uses it
Who usually picks 99.99%
Payments, auth, and infrastructure-facing products where minutes are the unit of pain.
Caveats
Read this before you print it on a sales slide
- False pages burn the humans who defend this SLA — consensus matters
- Dependency SLAs (cloud, DNS, CDN) eat your budget if you count them
FAQ
99.99% uptime, answered
Exact minutes for four nines, who should promise it, and why false pages hurt more at this target.
Keep reading
Related SLA and cost tools
- What counts as good uptime
99.9% vs 99.99% vs 99.999% in plain English.
- How to write an uptime SLA
Promises you can actually keep.
- Downtime cost calculator
Turn outage minutes into dollars.
- 99.9% uptime
8.8 hours / year
- 99.95% uptime
4.4 hours / year
- 99.999% uptime
5 minutes / year
Defend 99.99% with clearer pages
False pages waste the people who keep a 99.99% promise. Tallwatch opens incidents when at least two regions agree — Free includes consensus.