SLO and Error Budget Calculator
Turn an availability target into downtime or failed-request limits, then see how much budget remains.
What the calculator measures
An error budget is the part of a measurement window that may fail while a service still meets its objective. The calculation is 1 minus the SLO. A 99.9% target therefore leaves a 0.1% error budget.
For a 30-day window, 99.9% availability allows 43.2 minutes of downtime. For one million requests at the same target, the budget is 1,000 failed requests. Enter observed downtime or failures to see the percentage consumed and the amount left.
How to use the result
The number is useful only when the service has a written measurement window and a customer-facing indicator. Teams can use remaining budget to guide release decisions, reliability work, and incident review rather than arguing from general impressions.
This calculator handles both time-based availability and request-based success objectives. It runs entirely in the browser and does not submit the values you enter.
Put the number into an operating plan
Frequently asked questions
What is an error budget?
An error budget is the allowed failure portion of an SLO measurement window. It equals 1 minus the SLO, so a 99.9% objective leaves 0.1% for downtime or failed requests.
How much downtime does 99.9% allow in 30 days?
A 30-day window contains 43,200 minutes. A 0.1% error budget allows 43.2 minutes of downtime.
Should planned maintenance consume the budget?
Use the same rule your SLO document gives customers and teams. If users experience planned maintenance as downtime, count it. Document exclusions explicitly rather than removing them after the fact.
Is an error budget the same as an SLA?
No. An SLO is an internal reliability objective. An error budget turns that objective into allowed failure. An SLA is a customer agreement that may include remedies or credits.