Abstract:It is predicted that smartphone numbers will increase to 2.8B in 2018, up from around 2B in 2016. Moreover, revenue from application stores is predicted to reach $189B by 2020, up from $88.3B in 2016 1 . Software effort and size estimation are essential when it comes to project managers being able to manage and plan a project so as to prevent it from failing. The planning and development of mobile applications differs from other traditional software applications due to the characteristics of the mobile environment, high autonomy requirements, market competition, and many other constraints. Therefore, this paper presents the results of a Systematic Literature Review (SLR) concerning effort and size estimation models in mobile application development; this is followed by a summary of estimation techniques used across mobile apps. In particular, we focus on the software estimation models that are applicable to the Agile Software Development (ASD) process. The aim of this SLR is to provide researchers and practitioners with an overview of the current state-of-the-art software estimation techniques used in mobile applications. At the end of this review, some suggestions, research gaps and possible future work will be presented.