The strength of coal is usually determined by the tumbler tests and shatter tests. The strength index is an empirical and its numerical value cannot be used to predict the extent of breakage in a bulk handling circuit. A new drop test procedure has been developed to measure the strength of the coal based on the extent of the breakage due to repeatedly drop from a predetermined height. The lump size coal breaks in the tumbler drum by volume breakage and surface breakage; the extent of one affects the extent of other. Tumbler index is not directly related to any fundamental material property but depends on the number of lifters in the drum and material parameters, which include particle size and strength. The rate of degradation is higher on larger lump sizes coal compare to smaller lump size. At small drop heights, the stress of impact experienced by the sample sizes is comparatively smaller and resulting in a much lower extend of volume breakage and increase the significant of surface breakage. (c) 2004 Elsevier B.V. All rights reserved.