Structural defects are of significant importance in (electro)catalysis, as they provide sites of unusually high activity that find applications in many key electrochemical processes. However, tools to characterize surface defects remain scarce and complex, especially for nanocatalysts where classical methods such as transmission electron microscopy or X-ray scattering are limited in their ability to probe the structure and distribution of the active surface sites. Herein, we show that the ratio between the CO_ads stripping charge (Q_CO) and the charge required to desorb under-potentially deposited H atoms (Q_H) in structurally-disordered Pt-based nanocatalysts scales almost linearly with the Surface Distortion descriptor obtained via advanced physical methods. This trend is valid in both rotating disk electrode configuration and in a real fuel cell device, thus providing the scientific community with a powerful and versatile approach for semi-quantitative estimation of the surface lattice distortion in Pt-based catalysts without the need for exhaustive structural characterization.