Brier Calculator
A Brier score grades a forecast by how far your confidence was from the outcome. One forecast, one number: zero if you were certain and right, one if you were certain and wrong. Work through the three questions below and the calculator does the rest.
One falsifiable sentence, with a date or a threshold if it needs one.
Your probability that the forecast would come true, from 0 to 100.
Your journal
Nothing saved yet. Your forecasts will appear here, with a running average.
How to read the number
The Brier score is the squared distance between your probability and the outcome. Certainty that turns out wrong costs a full 1.0; hedging at 50 percent costs 0.25 either way. That asymmetry is the point: the score rewards knowing what you do not know, and it punishes confident mistakes hardest.
Below 0.10 is good. Around 0.20 is roughly where a thoughtful amateur lands. Above 0.30 usually means the forecasts were too confident for their evidence, not that the world was unfair.