Error Budget Calculator

An error budget is the amount of downtime you're allowed before you break your reliability target. If your SLO is 99.9% over a 30-day month, you're allowed 0.1% of that month down — about 43 minutes. That allowance is your error budget. It reframes reliability from 'never go down' to 'stay within budget', which lets teams balance shipping features against the risk of outages.

It's the chosen window multiplied by your allowed downtime fraction: window × (100 − target) ÷ 100. For 99.9% over a 30-day month that's 2,592,000 seconds × 0.001 ≈ 43m 12s. We then subtract the downtime you've already recorded for the window to show what's left. If you've used more than the budget, the remaining figure goes negative and you're over budget for the period.

That's exactly what continuous monitoring is for. This calculator gives you the budget; Uptimeify measures the actual downtime as it happens across your sites and services, so you always know how much error budget remains without doing the maths by hand — and you get alerted before you blow through it.