Every crypto chart site quotes a Fear & Greed number. Few say what is inside it. We built one from the futures market's own daily prices and wrote the method down so anyone can reproduce it. This post explains the four measures, the maths, how we checked it, and where it falls short.

What goes in

The index is the plain average of four scores. Each runs from 0 (extreme fear) to 100 (extreme greed), and each counts for 25%.

Volatility. Bitcoin's 30-day realised volatility: the standard deviation of its daily log returns, annualised. The score is 100 minus the percentile rank of today's value among the previous 365 days. Calm markets score high, turbulent ones low.

Momentum. How far Bitcoin's close sits above or below the average of its last 90 closes, ranked against the previous 365 days in the same way.

Breadth. The share of the 100 most traded altcoins whose close is above their own 30-day average. The share is the score.

Appetite.…