Rollout risk calculator
Put real numbers on a staged rollout before you ship it. Enter your traffic and your error rates to see the blast radius, a safer first step, and how long to watch it. Nothing you type leaves your browser.
Your blast radius
Fill in the four fields and calculate. The math runs here in your browser, so nothing you type is sent anywhere.
About these numbers
Where does the recommended rollout percentage come from?
It compares your new error rate to your baseline. Up to twice the baseline caps the first step at 5%, up to five times caps it at 1%, and anything worse caps it at 0.1%. It never suggests a wider rollout than the one you entered.
How is the monitoring window sized?
It is the time needed to see roughly 100 failing requests at the new error rate, with a floor of 15 minutes and a cap of 4 hours. Below about 100 failures, a rate change is hard to tell apart from normal noise by eye.
Do you store what I type here?
No. The calculation runs in your browser and no input is sent to us. The only thing that reaches our servers is an email address, and only if you submit the form yourself.
Is this a statistical significance test?
No. It gives you the order of magnitude of a rollout's blast radius so you can size the first step sensibly. Analysing a finished experiment is a different job.