In diagnostic radiology, entrance surface air kerma (ESAK) is one of the patient radiation dose quantities, and the effective dose is used as an estimator of possible risk for radiation exposure level. Calculation of the ESAK and effective dose requires both X-ray machine parameters and patient exposure parameters. Due to the high performance of smartphones and the increase in mobile applications, this study aimed to develop a mobile application to estimate the ESAK and effective dose in general radiography. The ESAK calculator was then developed using Android studio software, which is a standalone application operating on Android operating system version 5.0 or higher. X-ray machine parameters are initially required for calculating X-ray output. For the ESAK and effective dose calculation, exposure parameters for each examination are needed. The results showed that the average score of satisfaction was 4.64±0.13, which was very satisfactory. In conclusion, the ESAK calculator could be used for estimating ESAK and effective dose for individual radiographic examination.