A method of determining the installed equipment cost of a chemical plant. It is based on average cost data from nearly 50 industries involving both process industry and more general industry equipment costs. The cost at any particular time is based on the original cost at some earlier specified time multiplied by a ratio of cost indices for the present to the earlier time of interest. The base year is taken as 1926 with a value of 100. Until April 2012, the index was published in the monthly issues of the magazine Chemical Engineering.