Mineral processing is a vital part of mining projects and mainly involves comminution, sizing, concentration, extractive metallurgical processes, and dewatering. Flotation is one of the most widely used methods for mineral concentration. Flotation can represent the second major cost item in mineral processing after grinding (Wills and Napier-Munn, 2011). Accordingly, it is a main concern of mining project managers to select and optimize flotation circuits in order to decrease costs and increase productivity. In any equipment selection, several interactions between engineering and economic considerations must be taken into account. Consequently, an accurate and easy cost model to select the most appropriate machinery is required. Moreover, cost models could be used in flow sheet simulations applied in design and optimization. Models of unit operations built into the simulators could be improved by linking the equipment cost models (Khalesi et al., 2015).A number of approaches can be employed with the aim of developing the cost models. A review of these methods can be found in recent papers by Niazi et al. (2006) and Huang, Newnes, and Parry (2012). Regression is one the most frequently applied techniques for cost modelling (Smith and Mason, 1997). Several cost models have been established related to mining and milling projects ( Table I). One of the preliminary works was undertaken by Prasad (1969) and has been carried on in the recent work of Sayadi, Khalesi, and Khosfarman (2014). Almost all of these models have been developed based on exponential single regression approaches; correlating only one independent variable to a cost value (Stebbins, 1987). Consequently, in spite of the usefulness of these models in preliminary cost estimation, the role of other effective parameters has simply been overlooked. Some of these models have become old and updating them also may cause significant errors. Furthermore, these models mainly estimate total operating cost, and estimation of detailed operating cost items such as maintenance, lubrication, etc. is not possible. To overcome these deficiencies, this paper aims to introduce up-to-date capital and detailed operating cost models considering multiple effective factors of flotation machines. Two sets of single (SRA) and multiple regression (MRA) cost functions are presented. The first set is suitable for cost estimation at the initial phases of a project and is mainly appropriate for building rapid cost estimates where only one particular design factor of a flotation machine is accessible. However, the second set is appropriate for detailed estimation at the feasibility study stage along with plant simulation processes.Cost modelling for flotation machines by S. Arfania*, A.R. Sayadi* † , and M.R. Khalesi* Flotation is one of the most widely used operations in mineral processing plants and assumes a significant share of the total milling costs. The purpose of this paper is to introduce a new set of capital and operating cost models for major flotation machines based on th...