AbstractEstimation of Investment Costs in Process Development. This article gives an overview of plant cost estimating; the corresponding data and authors who have described the individual methods can be obtained from the primary literature. The definitions, the present authors, own data and experience gained in Germany, the pros and cons in practice of each cost estimating method are presented. The turnover ratios, capacity ratio exponents, step‐counting methods, and factor methods are emphasized for cost estimating in a situation of comparative uncertainty in the early stages of a project, because unit cost methods and detailed cost estimating are often used for budgetin