Volatility of volatility
How much does the size of a market's swings itself change from week to week?
In plain words
Volatility of volatility, often called vol of vol, measures how unstable a market's swing size is. It asks not how big the recent moves were, but how much those move sizes jumped around between one period and the next.
Why it matters
Risk models and position sizes usually assume a market's volatility is fairly steady. When swing sizes themselves shift sharply, a position sized for a calm pattern can become badly misjudged within a single week, and option prices, which depend on expected volatility, can move even when the underlying price barely does.
In a real week: BTC, week of 24 August 2026
In the week of 24 August 2026, BTC's realised volatility was 37.8% a year, its range was 6.27%, and its largest hourly move was -1.52% on Friday at 15:00 UTC. The prior four weekly returns were -2.8%, 2.09%, -3.08% and 23.58%, differing widely in size, though this week's data does not directly measure how much swing size changed.
A common mistake
Confusing vol of vol with volatility itself. Volatility describes how large recent price moves were; volatility of volatility describes how much those move sizes varied between periods, and can be high even when average swing size is modest.