SLO & error budget calculator
Turn an availability target into the downtime and failed requests you can afford, and the burn-rate alerts that protect it.
How it works
The error budget is the part of the window your service may fail: one minus the target, times the length of the window. A 99.9% target over 30 days leaves 0.1% of 43,200 minutes.
A burn rate of 1 spends the budget exactly over the window. Paging only when it burns many times faster, and only when a long and a short window agree, catches real outages quickly without waking anyone for a blip.
budget = (1 − target) × window
burn rate = error rate ÷ (1 − target)Questions
What's the difference between an SLO and an SLA?
An SLO is the target you hold yourself to. An SLA is a promise to customers with consequences, usually set looser than the SLO.
Which window should I use?
Rolling 28 or 30 days is common: long enough to smooth noise, short enough that a bad week still matters.
What happens when the budget runs out?
Teams usually slow risky releases and spend time on reliability until the window recovers.