Spectra matching is widely used in various applications including the search for a spectrum of an unknown or subject material, chemical, or compound in an existing spectral database and quality control by means of comparing the spectra of products with standards. New systems and methods are described for identifying an unknown compound by calculating the similarities of Fourier-transform infrared (FTIR) spectra of organic compounds. The systems and methods incrementally calculate the spectral similarity based on the local spectral shapes. This reduces the bias caused by uneven weighing of large or broader peaks. In addition, the new systems and methods tolerant to the common issues in spectra matching including baseline offset, baseline sloping, and deviations in wavenumber axis alignment, suggesting its robustness and practical applicability.