GSim is a software for NMR spectroscopy, a free program tool for visualisation and processing of experimental and simulated nuclear magnetic resonance (NMR) spectra. Historically GSim was started as an extension of SIMPLOT which would be able to represent 2D NMR spectra along with 1D.

But later several processing functions and import filters for some commercial file formats have been added. Currently Chemagnetic/Varian Spinsight, Bruker XWin-NMR/Top-Spin, SPINEVOLUTION, Varian VNMR and SIMPLOT formats should work.
GSim is a highly-featured and strong visualisation and processing tool for (solid-state) NMR data.

It is aimed to be a flexible and convinient program for NMR (solid-state NMR in particular) specialists and advanced users. In contrast to many other NMR program tools it should provide more flexibilty and extendabilty. As a drawback, it could looks slightly overcomplicated for occasional NMR users.

GSim Features:
1. Easy visual overlapping of 1D or even 2D spectra
2. Zooming/shifting/etc. by simple mouse drag.
3. "One-click" full processing from a predefined processing list
4. Fourier transformation in one and two dimensions (using TPPI or STATES for indirect dimension).
5. Resizing, shearing, cyclic shift etc.
6. Phasing, gaussian and exponential apodizations
7. Spectrum editing (summation, scalings)
8. Deconvolution (peak fitting)
9. Estimation of the linewidth and integration
10. Peak peaking
11. Easy (copy-paste) export of data to external applications as MS Excel or Origin.
12. Other conventional (and not only conventional) NMR functions.

The interface consists of the main plot area and several movable side panels. The main plot window can display either 1D or 2D NMR data, depending on what kind of data is currently active (see below for the active dataset definition).

The license of this software is Free, you can free download and free use this calculator software.