Capital cost assessment is an integral part of an evolving process design. The assessment should consider installed equipment costs inclusive of plant bulk items and not solely purchased equipment costs. The ratio of installed equipment cost to purchased equipment cost varies much more widely for individual equipment items than for entire plants; the ratio depends on equipment class, design, size and construction materials as well as plant layout. The factored (IChemE) method outlined in the Institution of Chemical Engineers 'blue booklet' is of immediate use and provides a basis for checking detailed estimates. Some experience in the application of the IChemE method by the authors is reviewed. Recommendations are made for broadening the inputs for estimating, and some factors are proposed for estimating installed costs of equipment of different classes. Quantitative data are also presented for cost breakdown in entire plants arising from project reviews by the authors.