A Python package for flavour physics phenomenology in the Standard Model and beyond


State-of-the-art predictions for hundreds of observables, both in the Standard Model and for arbitrary new physics effects (parametrized as Wilson coefficients of dimension-6 operators)


Fit parameters or Wilson coefficients to a host of experimental data included in the package, or supplied by you


Visualize predictions or fit results in publication quality using flavio's predefined plot functions built on the power of matplotlib

Easy to install

Thanks to Python, no compilation is necessary, even when you make changes to the code

Easy to customize

By modifying simple text files, you can change input parameters or choose between different implementations, e.g. for hadronic form factors


Using Jupyter, you can access (or modify!) all the features of flavio in an interactive session (similar to Mathematica)

Featured processes

  • $B^0$, $B_s$, and $K^0$ mixing
  • $B\to K^{(*)}\mu^+\mu^-$ and other exclusive rare $B$ decays
  • Inclusive decays $B\to X_{s,d}\gamma$ and $B\to X_{s,d}l^+l^-$
  • Lepton flavour violating $B$ decays
  • $B\to D^{(*)}\tau\nu$ and other tree-level $B$ decays
  • $K\to \ell\nu$, $K\to \pi\ell\nu$, and $K\to \pi\nu\bar\nu$ decays

License & disclaimer

The code is released under the MIT license. As such, it is provided “as is” without any warranty.

If you use flavio in a project, please cite:


The theme of this web site is based on devAid by Xiaoying Riley, licensed under CC BY 3.0.


Main developer: David Straub

Please file bug reports and make feature requests over at Github