The 25-delta risk reversal is the implied-volatility gap between an out-of-the-money call and an out-of-the-money put at the same distance from spot. It is one of the cleanest read-outs of directional positioning in crypto options: when puts carry richer implied vol than equivalent calls, the market is paying up for downside protection (fear); when calls are richer, it is paying up for upside exposure (greed). Read as a level and as a change over time, the risk reversal tells you which side of the tail traders are hedging, a signal that often moves before spot does.
What is options skew?
If every option on an asset were priced off a single "fair" volatility, a plot of implied volatility against strike would be a flat line. In real markets it is not flat. Out-of-the-money options usually trade at different implied volatilities than at-the-money ones, and the puts and calls are rarely symmetric. That asymmetry is skew.
Skew exists because option demand is not balanced. Different participants want different protection. The price of an option is, in part, the price of the insurance it provides, and the side of the market that more people want to insure against trades at a higher implied volatility. Skew is therefore a positioning signal hiding inside a pricing surface: it shows where the crowd is willing to pay up.
The full picture across all strikes is the volatility smile (or smirk). The risk reversal is a way to compress that whole curve into a single, comparable number.
What is the 25-delta risk reversal?
The 25-delta risk reversal is the implied volatility of a 25-delta call minus the implied volatility of a 25-delta put for the same expiry:
Risk reversal = IV(25Δ call) − IV(25Δ put)
Delta is roughly the option's sensitivity to spot and a loose proxy for the probability it finishes in the money. A 25-delta call and a 25-delta put sit at comparable distances out of the money on either side of spot, close enough to be liquid and actively traded, far enough out to reflect genuine directional bets rather than at-the-money noise. That balance is why the 25-delta points, rather than the 10-delta tails or the at-the-money strike, are the conventional gauge.
