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<h2 class="subheader-headline">Fast &amp; Accurate Option Analytics</h2>

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Option Pricing &bull; Implied Volatility &bull; Greeks<br/>

Python package: vollib 1.0.7 &bull; TypeScript package: vollib<br/>

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<a href="https://vollib.tsukuro.dev/">Try the TypeScript browser demo</a>

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Vollib is a family of libraries for calculating option prices, implied volatility, and greeks.

The current Python package is <code>vollib</code> 1.0.7 and later. It supports Python 3.9 through

3.12 and should be installed with <code>pip install -U vollib</code>.

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Existing <code>py_vollib</code> installs and imports continue to work through a deprecated transition

package and compatibility namespace, but new Python code should import from <code>vollib</code>.

The temporary <code>vollib-test</code> package is superseded by the official release.

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What makes vollib special is that it is built around Peter Jäckel's LetsBeRational, a fast and

accurate technique for obtaining Black implied volatility from option prices. LetsBeRational is

designed to reach machine precision in at most two iterations, and usually one, on standard 64-bit

floating point hardware.

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Building on this solid foundation, vollib provides functions to calculate option prices, implied

volatility and greeks using Black, Black-Scholes, and Black-Scholes-Merton. vollib implements both

analytical and numerical greeks.

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<h3 class="small-title">Sponsors</h3>

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<a href="https://finance.ikayzo.com"><img src="images/ikayzo-logo.svg" class="sponsor-image ikayzo" alt="ikayzo logo"/></a><br>

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<a href="https://github.com/vollib/lets_be_rational">LetsBeRational</a> was originally written in C++.

The legacy Python package, <code>vollib</code> 0.1.x, used the SWIG-wrapped implementation and targeted

Python 2.7.

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The <code>py_vollib</code> package name was introduced during the Python 3 transition. Starting with

version 1.0.7, the canonical Python package name is again <code>vollib</code>. The old Python 2.7 line

remains available only for pinned legacy installs.

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<h3 class="small-title">Technical Note</h3>

<p>

A strictly positive strike price is part of vollib's supported input domain for Black, Black-Scholes,

and Black-Scholes-Merton calculations. This preserves the behavior of the LetsBeRational-backed

implementation; callers who want to support limiting cases such as a zero-strike call should handle

those boundaries in application code.

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TypeScript, Java, and JavaScript repositories are listed on the Source page. The Python API

documentation for <code>vollib</code> 1.0.7 is available on the Documentation page.

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If you use any version of LetsBeRational or Vollib we would be most grateful if you would kindly

give credit by linking back to this page.

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&copy; 2026 Larry Richards

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