Single-molecule force spectroscopy has proven to be an efficient tool for the quantitative characterization of flexible foldamers on the single-molecule level in this study. The extent of folding has been estimated quantitatively for the first time to the best of our knowledge, which is crucial for a better understanding of the "folding-process" on single-molecule level. Therefore, this study may provide a guidance to regulate folding for realizing rational control over the functions of bulk materials.