In the last years, interest in the study of the relationship between the magnetic helicity of solar active regions and the one contained in the interplanetary structures has grown. This has lead us to compute the helicity content of an interplanetary hot tube observed by Wind on October 24–25, 1995, applying three different approaches in cylindrical geometry: a linear force‐free field, a constant twist angle, and a non force‐free model with constant current. We have fitted the set of free parameters for each of the three models, finding that the determined magnetic helicity values are very similar when using the same orientation for the flux tube. From our point of view, these results imply that, whatever be the model used, magnetic helicity is a well‐determined quantity and, thus, it is worth using it to understand the link between solar and interplanetary phenomena. © 2003 American Institute of Physics