  We present here the signal-to-noise (S/N) calculator developed for the
Colorado Ultraviolet Transit Experiment (CUTE) mission. CUTE is a 6U CubeSat
operating in the near-ultraviolet (NUV) observing exoplanetary transits to
study their upper atmospheres. CUTE was launched into a low-Earth orbit in
September 2021 and it is currently gathering scientific data. As part of the
S/N calculator, we also present the error propagation for computing transit
depth uncertainties starting from the S/N of the original spectroscopic
observations. The CUTE S/N calculator is currently extensively used for target
selection and scheduling. The modular construction of the CUTE S/N calculator
enables its adaptation and can be used also for other missions and instruments.
