There exists a fundamental tradeoff between spectral resolution and the efficiency or throughput for all optical spectrometers. The primary factors affecting the spectral resolution and throughput of an optical spectrometer are the size of the entrance aperture and the optical power of the focusing element. Thus far collective optimization of the above mentioned has proven difficult. Here, we introduce the concept of high-throughput computational slits (HTCS), a numerical technique for improving both the effective spectral resolution and efficiency of a spectrometer. The proposed HTCS approach was experimentally validated using an optical spectrometer configured with a 200 um entrance aperture, test, and a 50 um entrance aperture, control, demonstrating improvements in spectral resolution of the spectrum by ~ 50% over the control spectral resolution and improvements in efficiency of > 2 times over the efficiency of the largest entrance aperture used in the study while producing highly accurate spectra.