> For the complete documentation index, see [llms.txt](https://guide.laevitas.ch/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://guide.laevitas.ch/laevitas-metrics/10d-25d-butterfly.md).

# 10Δ 25Δ Butterfly

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This metric shows the historical 25-Delta Butterfly values across different time periods by rolling maturity.
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Butterfly is the difference between the average volatility of the call price and put price with the same moneyness level (25-Delta) and the ATM volatility level. For instance a BF 25 could be expressed by the following formula:\
\
BF25 = (σ25C + σ25P) /2 – σATM\
\
Butterfly spreads measure the curvature (kurtosis). The higher the Butterfly spreads, the more ‘peaked’ is your implied volatility curve.