---
title: "Five Nines (99.999% uptime) — monitoring glossary"
description: "Five nines of availability means 99.999% uptime — a service level that allows no more than 5 minutes 15 seconds of downtime per year. It is the gold standard…"
canonical: "https://lemwatch.com/glossary/five-nines"
source: "https://lemwatch.com"
---

# Five Nines (99.999% uptime)

> Five nines of availability means 99.999% uptime — a service level that allows no more than 5 minutes 15 seconds of downtime per year. It is the gold standard for telecom and critical infrastructure but is rarely achievable, or economically justified, for…

## Definition

 Each additional nine reduces allowed downtime by a factor of ten. 99% (two nines) allows 3.65 days of downtime per year, 99.9% (three nines) allows 8.77 hours, 99.99% (four nines) allows 52.6 minutes, and 99.999% (five nines) allows just 5.26 minutes.

 Reaching five nines requires multi-region failover, automated incident response, redundant networking, and zero single points of failure. It is expensive — usually 10x to 100x the cost of running at 99.9% — and rarely justified outside of payments, telecom, and life-critical systems.

## Why it matters

 Most SaaS contracts specify three nines or four nines. Knowing what nines you actually need stops you from over-engineering — and lets you call out vendor SLAs that quietly only commit to 99% (3.65 days a year of permitted outage).

 See it in the product: [Public status pages](https://lemwatch.com/status-pages).


## Related

- [Monitoring glossary](https://lemwatch.com/glossary)
- [Uptime](https://lemwatch.com/glossary/uptime)
- [SLA](https://lemwatch.com/glossary/sla)
- [Downtime](https://lemwatch.com/glossary/downtime)
- [MTTR](https://lemwatch.com/glossary/mttr)
- [All monitoring checks](https://lemwatch.com/features)
- [HSTS (HTTP Strict Transport Security)](https://lemwatch.com/glossary/hsts)
- [False Positive](https://lemwatch.com/glossary/false-positive)