The aim of this applied study has been to demonstrate how a cost calculation is done in a systematic way. The framework of the project has been limited to older nuclear installations in Sweden. Furthermore, it may be envisaged that the process of making regular estimates of all the parameters is crucial in preparatory phases of decommissioning and dismantling processes. A secondary aim of the presented project has been to define and present a comprehensive procedure for how to prepare an overall description of all qualified input data that ought to be used in the earlier planning phases of decommissioning projects. Such parameters as costs, exposure times, duration times, amounts of waste, manpower and manpower allocation as well as equipment needed has to be estimated.