Uptime & error budget calculator
Free, no sign-upWhat does 99.9% uptime allow? Work out your downtime budget and see how much is left.
Target and outages
Downtime budget
- Allowed downtime
- Downtime used
Time-based estimate, not proof of SLA compliance. Count each unavailable minute once.
Downtime breakdown and other targets
- Scenario uptime
- Outage time
- Maintenance counted
- Eligible time
- More outages of this length within budget
| Target | Downtime allowed | Budget left |
|---|
Calculation and limits
Allowed downtime = eligible period minutes × (1 − target / 100). Used budget = incident count × full outage duration, plus maintenance when included. Remaining = allowed − used.
Count each unavailable minute once. Incidents and maintenance must not overlap. The calculator uses elapsed time, not request-based availability, and does not replace your SLA's exclusions, service-credit rules or monitoring evidence.
Your answers and calculations stay in your browser. Shared links include your inputs. Only share information you are happy to pass on.
A little more detail
What does 99.9% actually allow?
Over 30 days, 99.9% uptime leaves 43 minutes and 12 seconds of downtime. That is the whole allowance, not the allowance for each incident.
Compare alert detection timesIs an uptime target the same as an SLA?
An internal target is often called an SLO. An SLA is an agreement that defines measurement, exclusions and consequences. This calculator converts a time-based target into minutes; it does not interpret a contract.
Should planned maintenance count?
Use the rule that matches your target or agreement. For the customer's experience, planned downtime is still downtime. Some agreements exclude it, so make that choice explicit when comparing results.
Can I use this for a real calendar month?
Choose the period length that matches your reporting window. Month lengths differ, so a fixed 30-day budget is not identical to February or a 31-day month.
Keep an eye on your website
Let Scavo do the regular checks.
Get uptime alerts and weekly health checks, with findings you can send straight to your web team.