Put an outage in context.
Availability calculator and incident response guides
Availability arithmetic and practical incident-record guides for small web teams. Clear measurement windows, explicit exclusions and reproducible calculations.
Website availability and downtime calculator →Quick availability calculator
Enter any uptime percentage. See exactly how much downtime that buys you — per month and per year.
Same arithmetic as the uptime math guide. Models are planning tools, not guarantees.
The ladder of nines, on the site's 30-day month (43,200 minutes). The steps are ÷10, ÷2, ÷5, ÷10 — not a tenth each — so the multipliers are printed on the rungs and the rungs keep one uniform size.
Make the next decision clearer.
More availability guides
What uptime percentages mean
Convert each nine into downtime minutes.
Read the guide →AVAILABILITY GUIDESLA vs SLO vs SLI
Separate measurement, internal targets, and promises.
Read the guide →AVAILABILITY GUIDEIncident response runbook template
Record decisions while the incident is still fresh.
Read the guide →AVAILABILITY GUIDEMTTR and MTBF explained
Use repair and failure intervals with clear limits.
Read the guide →Begin with your own evidence
Calculate observed availability from a defined measurement window and recorded downtime. Compare it with a target without treating a target as a guarantee.
Availability = (window minutes − downtime minutes) ÷ window minutes × 100. Allowed downtime at a target = window minutes × (1 − target ÷ 100). A 30-day window contains 43,200 minutes; 30 minutes downtime means 99.93056% observed availability.
The tool assumes the downtime total is correct and non-overlapping. Probe failures, partial outages, planned maintenance and contractual exclusions need a defined measurement policy. A result does not establish an SLA credit or prove a service was available to every visitor.
How we prepare these resources →