This paper proposes a calculation model for estimation of uncertainty of offshore Cone Penetration Test (CPT) measurements. The model considers CPT definitions and recommendations included in ISO standard 19901-8 Marine Soil Investigations. Particularly, this standard defines (1) application classes for CPT equipment selection and intended use of results, (2) accuracy of CPT parameters as uncoupled from spatial position and (3) true values depending on deployment-specific features. Estimates of measurement uncertainty are presented for cone resistance, sleeve friction and pore pressure. The estimates consider non-drilling, vessel drilling and seafloor drilling as deployment modes. Results suggest that the application classes suit uniform, favorable site conditions. Example cases for adverse conditions illustrate potential difficulty in demonstrating agreement with any of the application classes.