The authors present GNSS-IR-UT, a MATLAB-based GNSS software that focuses on GNSS Interferometric Reflectometry (GNSS-IR) to estimate the absolute vertical distance from a GNSS antenna to the reflective surface using signals from GPS, GLONASS, Galileo, and BeiDou systems. This user-friendly software, equipped with a Graphic User Interface (GUI), processes signal-to-noise ratio (SNR) data from various GNSS systems (GPS, GLONASS, Galileo, BeiDou) and translates it into reflection height. Notably, the software allows users to assess different processing options and parameters for height calculation. The Least Square Harmonic Estimation (LS-HE) is employed for the first time in this software to extract the dominant frequency in the reflectometry concept.