The hydrogen compatibility of metallic materials is often evaluated by conducting tensile tests of H-charged specimens in air or inert gas at ambient temperature; however, it is not clear whether the H distribution calculated with hydrogen diffusivity under a diffusion-controlled process is consistent with the actual distribution. This study estimated the hydrogen distribution in a H-charged nickel maintained in air at ambient temperature for a few months after exposure to hydrogen gas by using the Vickers hardness test and secondary ion mass spectrometry. Both methods provided similar H distributions, which were fitted by the solution of a diffusion equation under a diffusion-controlled process, and the hydrogen diffusivity was also determined. The estimated H distributions were successfully fitted by the solution of the diffusion equation, and the determined hydrogen diffusivity of nickel was consistent with literature data, indicating that the calculated H distribution reproduced the actual one. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.