The most applied sterilisation method in healthcare for sterilisation of medical devices is steam. It is shown in literature, that sterilisation practices today are not completely understood [1, 2]. Literature defines “sterile” as “free of all viable organisms” [3]. Conditions to obtain sterile devices in steam sterilisation are specified in the literature [4] and standards [5]. In practice, however, it is noticed that the duration of a steam sterilisation process varies. Although the literature and standards indicate the success of a process depends on the combinations of the steriliser process, load contents, loading pattern and wrapping [5–7], no literature is found that explains the correlation between the weight of the load and the duration of the process.