WillItFit is an analysis tool for refining constrained structural models from small-angle scattering data. It relies on standard minimisation methods to find models of maximum likelihood from (several sets of) data. The code is open source and written with a focus on flexibility and customisability. In particular, models written in C can be added to the library using the outlined formalisms.

The inner workings of the software are described in the publication:
M.C. Pedersen, L. Arleth and K. Mortensen J. Appl. Cryst. 46, 1894-1898 (2013)

This software is developed, and maintained, by Martin Cramer Pedersen and other group members. The code repository of the stable version of WillItFit is hosted on the Sourceforge page of WillItFit.

There is also a branch of WillItFit which is designed for proteins with modifications as well as other (unstable) branches of WillItFit developed in the group on the GitHub page of WillItFit.