Where the sole object of applying insulation to a portion of plant is to achieve the minimum total cost during a specific period (evaluation period), the appropriate thickness is usually termed as the economic thickness. The principle is to find at what thickness further expenditure on insulation would not be justified by the additional financial saving on heat to be anticipated during the evaluation period. Although an increase in the amount of insulation applied will raise the initial installed cost, but it will reduce the rate of heat loss through the insulation. Therefore it is necessary to reduce the total cost during the evaluation period. In this work, simple-to-use novel correlation is formulated to arrive at the economic thickness of hot insulation suitable for process piping and equipments. The correlation is a function of pipe diameter and thermal conductivity of insulation for hot surface temperatures at 100°C, 300°C, 500°C and 700°C. A simple interpolation formula generalizes this correlation for wide range of hot surface temperatures. The proposed correlation covers pipeline diameter and hot surface temperature up to 0.5 m and 700°C respectively. The average absolute deviation percent of proposed correlation for estimating the economic thickness of the hot insulator is 2.12% demonstrating the excellent performance of proposed correlation. Simple-to-use approach can be of immense practical value for the engineers and scientists to have a quick check on the optimum insulation thickness for wide range of conditions. In particular, practice engineers would find the proposed approach to be user friendly involving no complex expressions with transparent calculations.