I currently conduct my research about evaluating the quality of reading materials. Since I teach students whose English is not their first or second language, I find it curious in using the formula to determine the level of text difficulty(readability). As far as I concern that the formula such as Fry, Flesch-Kincaid, Dhale etc. are provided for ESL students. Consequently, I wonder if these formula appropriate or not for my students context. What best reasons should be used to evaluate that of readability index for EFL learners using those formula? or is there any formula that might be used for EFL learners?