Availability math
SLA, uptime, and error budget calculator
Translate uptime targets into concrete downtime budgets, or enter a real outage duration to see the resulting availability for daily, weekly, monthly, and yearly windows.
Forward calculator
Choose a target availability/SLO to calculate allowed downtime.
Reverse calculator
Enter outage time to calculate achieved availability.
Examples: 1h 20m, 3 days 4 hours, 15m 30s, 45s, PT1H20M.
Business-hours mode
Weekday-only calculations are useful when an internal service promise excludes nights and weekends.
Nines reference table
| Target | Daily | Weekly | Monthly | Yearly |
|---|---|---|---|---|
| 90% | 2 hours 24 minutes | 16 hours 48 minutes | 3 days 1 hour 2 minutes 54.6 seconds | 36 days 12 hours 34 minutes 55.2 seconds |
| 99% | 14 minutes 24 seconds | 1 hour 40 minutes 48 seconds | 7 hours 18 minutes 17.5 seconds | 3 days 15 hours 39 minutes 29.5 seconds |
| 99.9% | 1 minute 26.4 seconds | 10 minutes 4.8 seconds | 43 minutes 49.7 seconds | 8 hours 45 minutes 57 seconds |
| 99.99% | 8.6 seconds | 1 minute 0.5 seconds | 4 minutes 23 seconds | 52 minutes 35.7 seconds |
| 99.999% | 0.9 seconds | 6 seconds | 26.3 seconds | 5 minutes 15.6 seconds |
| 99.9999% | 0.1 seconds | 0.6 seconds | 2.6 seconds | 31.6 seconds |
SLA
A Service-Level Agreement is an external promise to customers. Do not offer a contractual SLA unless legal, support, and billing terms are ready.
SLO and SLI
A Service-Level Objective is the internal target. A Service-Level Indicator is the measured data, such as successful checks divided by total checks.
Error budget
The error budget is the amount of downtime or failed checks left before the target is missed. Teams use it to decide when to slow releases and stabilize.
How ErrorNotifier fits
Free workspaces start with one ping every 15 minutes. Paid plans can move to five-minute, two-minute, or one-minute checks, add Slack and verified webhooks, and keep longer history for reviews.
Public demo
Review the real product screens with read-only mock data
Open the demo workspace to inspect monitors, incidents, domains, alert channels, status pages, projects, issues, automated test runs, releases, artifacts, audit history, and umbrella reports without creating an account.