Direct Answer
The 25-delta risk reversal is the implied volatility of the 25-delta call minus the implied volatility of the 25-delta put for one expiry. It summarizes the skew, meaning which side of the smile is priced higher. A negative value means downside puts are priced at higher implied volatility than upside calls, which is the usual pattern for equity indexes.
25-Delta Risk Reversal: Formula, Meaning, Signals, Examples and How to Use It
How Is 25-Delta Risk Reversal Calculated?
The 25-delta risk reversal is the implied volatility of the 25-delta call minus the implied volatility of the 25-delta put for one expiry. It summarizes the skew, meaning which side of the smile is priced higher.
Formula: RR25 = IV_25dCall - IV_25dPut
Inputs:
- Implied volatility of the 25-delta call
- Implied volatility of the 25-delta put
- A single expiry
Worked example. With a 25-delta call at 21% and a 25-delta put at 25%, the risk reversal is -4.0% in volatility points. The inputs are illustrative numbers, not market data.
Reading it. A negative value means downside puts are priced at higher implied volatility than upside calls, which is the usual pattern for equity indexes. A positive value means upside calls are richer. The sign convention is not universal, so confirm which leg is subtracted.
Limits. The sign convention varies by source, and the number depends on the expiry and on how delta is computed. It is a statement about option pricing, not a forecast of direction.
What is 25-Delta Risk Reversal?
The 25-delta risk reversal is the implied volatility of the 25-delta call minus the implied volatility of the 25-delta put for one expiry. It summarizes the skew, meaning which side of the smile is priced higher.
How to use 25-Delta Risk Reversal
A negative value means downside puts are priced at higher implied volatility than upside calls, which is the usual pattern for equity indexes. A positive value means upside calls are richer. The sign convention is not universal, so confirm which leg is subtracted. A reading alone is never a buy or sell signal; it needs context from price structure, volume, volatility and the broader market regime.
Strengths
- A direct difference between two implied volatilities of one expiry, quoted in volatility points, whose sign shows which wing is priced higher.
- Holding delta fixed at 25 keeps the two wings symmetric in option sensitivity, which makes it a clean skew gauge across dates.
- Reproducible when the formula and data convention are fixed.
Weaknesses and limitations
- It measures only the gap between the wings, so a parallel rise in both leaves it unchanged even though overall volatility moved.
- A change can come from either leg moving, so the number alone does not say whether calls or puts were repriced.
- Correlated indicators can create false confidence by repeating the same underlying information.
Editorial and risk note
This page is educational content, not individualized investment advice. It should not imply guaranteed prediction, accuracy or outperformance.
Frequently Asked Questions
Is 25-Delta Risk Reversal a buy or sell signal?
No. A negative value means downside puts are priced at higher implied volatility than upside calls, which is the usual pattern for equity indexes. The sign convention varies by source, and the number depends on the expiry and on how delta is computed. A trade built on it still needs a trigger, an invalidation rule, a position size and realistic execution assumptions.
What is the best setting for 25-Delta Risk Reversal?
25-Delta Risk Reversal is computed from implied volatility of the 25-delta call; implied volatility of the 25-delta put; a single expiry, so the choices that matter are the data convention and the window it is read over. Test those across instruments, regimes and out-of-sample periods instead of fitting one historical winner.
Can 25-Delta Risk Reversal be used by itself?
The sign convention varies by source, and the number depends on the expiry and on how delta is computed. It is a statement about option pricing, not a forecast of direction. For that reason it is read next to measures of direction, participation, valuation, liquidity and risk, not alone.
Does 25-Delta Risk Reversal work on every timeframe?
The calculation (RR25 = IV_25dCall - IV_25dPut) can be run on any bar size, but behavior is not portable: a reading on a five-minute chart describes a very different market window from the same reading on a daily chart. Validate the exact timeframe before relying on it.
Why does 25-Delta Risk Reversal give false signals?
It measures only the gap between the wings, so a parallel rise in both leaves it unchanged even though overall volatility moved. A change can come from either leg moving, so the number alone does not say whether calls or puts were repriced. Lag, noise and regime changes add to this, because market participants react to new information after the reading is calculated.
How should 25-Delta Risk Reversal be backtested?
Rebuild 25-Delta Risk Reversal from implied volatility of the 25-delta call using point-in-time data, write the rules before testing, include delisted securities where relevant, model realistic fills and costs, reserve a validation sample and compare with a simpler baseline.