Tool review: September 10, 2026.
This calculator translates an availability target into a simple time budget for the selected number of days. It is useful for planning and sanity checks, but a contractual SLA may use request-based availability, exclusions or measurement sources that produce a different result.
What the calculator does
Allowed downtime = period duration × (1 − availability target)
For a 30-day period, the tool converts the period to minutes and applies the unavailability fraction. The result is a mathematical budget, not permission to schedule an outage of that length.
Why SLA wording matters
Contracts can define maintenance windows, regional scope, excluded events, measurement granularity and credit thresholds. A generic percentage cannot reproduce those legal and operational rules. Use the agreement’s own language when producing an official report.
SLA vs SLO
An SLA is a contractual commitment with defined remedies or terms. An internal SLO is an engineering target used to manage reliability. Both can use percentages, but the consequences and calculation rules are different.
Use the budget operationally
- Track remaining error budget over the same reporting window.
- Record incidents that consumed the budget and their user impact.
- Investigate repeated short failures even when the aggregate percentage still passes.
- Do not round away small but material outages before applying the agreed method.
Related resources
SLA math needs a written measurement rule
The same percentage can produce disputes if the contract and monitor count time differently. Before relying on the allowance, document the reporting window, timezone, planned-maintenance treatment, rounding, partial failures and source of truth. Keep the raw incident timestamps so the percentage can be reproduced later.