SLA Uptime and Downtime Calculator
Convert an SLA target into real allowed downtime by period, with a business-hours option and copy-ready snippets.
What this calculator does
Takes an SLA uptime target (for example 99.9% or 99.95%) and converts it into the exact downtime permitted over a chosen period. Switch to business-hours mode to base the calculation on your operating hours instead of 24×7.
Results include a table for common windows (day, week, 30 days, quarter, year) and copy buttons that produce clause-ready text for a runbook or SLA.
A concrete example
At 99.95% availability measured over 30 days, the permitted unavailability is 21 minutes 36 seconds. The same target over 365 days allows 4 hours 22 minutes 48 seconds.
SLA vs SLO
An SLA is a customer-facing commitment that may include credits or remedies. An SLO is an internal reliability target. This calculator turns a target percentage into allowed downtime; pair it with the SLO and error budget calculator for operating decisions.
Put the number into an operating plan
Frequently asked questions
Does business-hours mode change the percentage?
No. It changes the denominator. Instead of measuring against 24×7 time, the calculator multiplies your business hours per day by your business days per week and scales to the selected period.
Which “month” does 30 days represent?
This calculator uses a 30-day window as a common industry baseline for availability targets. If your contract specifies a different window (calendar month or 28 days), pick the matching period or use the week/year values.
Is this the same as an SLO?
No. SLOs are internal objectives; SLAs are promises to customers. Use this tool to size downtime allowances and the SLO/Error Budget calculator to manage release and remediation decisions.