Software package SASfit
for fitting small-angle scattering curves

SASfit has been written for analyzing and plotting small angle scattering data. It can calculate integral structural parameters like radius of gyration, scattering invariant, Porod constant. Furthermore it can fit size distributions together with several form factors including different structure factors. Additionally an algorithm has been implemented, which allows to simultaneously fit several scattering curves with a common set of (global) parameters. This last option is especially important in contrast variation experiments or measurements with polarised neutrons. The global fit helps to determine fit parameters unambiguously which by analyzing a single curve would be otherwise strongly correlated. The program has been written to fulfill the needs at the small angle neutron scattering facility at PSI ( The numerical routines have been written in C whereas the menu interface has been written in tcl/tk and the plotting routine with the extension blt.

Author Information:


by Joachim Kohlbrecher
and Ingo Bressler

Laboratory for Neutron Scattering
Paul Scherrer Institut
CH-5232 Villigen PSI
Tel: +41 56 310 3165
Fax.: +41 56 310 20 87

SASfit is available for users analysing data taken at PSI
SASfit has been developed at the Paul Scherrer Institute (PSI) and remains copyright of the PSI.
SASfit is provided for users of the PSI facilities
SASfit is provided "as is" and with no warranty.

download SASfit package: (source, Windows binary , Linux binary, MacOS binary)
(previous versions)

Manual with a jumble of formulas used by SASfit (pdf, html)
Video about “How to set up the build environment
Video about “How to Create a New Plugin

Version information:


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