Error Budget Calculator
Turn any SLO into a concrete error budget — downtime minutes or failed requests — for your window, then track how much you've already burned and whether you're still in the green.
Runs entirely in your browser. Nothing is sent to a server.
Why error budgets beat “never go down”
Demanding 100% uptime stalls engineering — every release becomes a risk with no allowance for failure. An error budget reframes reliability as a quantity you can spend. As long as budget remains, the team ships features and runs experiments freely; when it runs low, the priority automatically shifts to stability. The budget is simply the inverse of your SLA / uptime target — if you have not set one yet, start there.
You can only spend a budget you can measure
A 99.95% SLO leaves roughly 22 minutes a month. To manage that you need real uptime monitoring, an accurate record of every outage, and fast alerting so a high burn rate pages someone before the budget is gone. When an incident is over, capture what happened with a post-mortem report so the same budget isn't spent twice on the same bug.
Frequently asked questions
What is an error budget?
An error budget is the amount of unreliability your SLO permits. If your SLO is 99.9% over 30 days, you are allowed to be down 0.1% of the time — about 43 minutes 50 seconds. That allowance is your error budget: spend it on risky releases and maintenance, and stop shipping when it runs out.
How do you calculate an error budget?
Error budget = (1 − SLO) × total. For a time-based SLO, total is the length of the window: a 99.95% SLO over 30 days gives (1 − 0.9995) × 43,200 minutes ≈ 21 minutes 55 seconds. For a request-based SLO, total is your request count: 99.9% of 1,000,000 requests allows 1,000 failures.
What is error budget burn rate?
Burn rate is how fast you are consuming the budget relative to the window. A burn rate of 1 spends the entire budget exactly over the window; a burn rate of 10 would exhaust a 30-day budget in 3 days. High burn rates are what good alerting watches for, because they catch a degradation before the SLO is formally breached.
Does this calculator store my SLO data?
No. Everything runs locally in your browser. No SLO, request count, or downtime figure is sent to any server.
Watch your burn rate in real time
Alert24 tracks uptime, opens incidents automatically, and pages on-call the moment your error budget starts burning fast — not after it's gone.