The industry of software should be efficient. Due to rapid change in technology, implementation of complex software systems at cheaper cost and the urge to maintain better quality software are some of the major challenges for the software companies. One of the toughest works is cost estimation, in the field of software engineering. It is the estimation of total cost required in developing software. Researchers have proposed various methods of cost estimation. This paper gives an insight into the various models and techniques used in estimating cost of the software. The benefits and drawbacks of the existing cost estimating techniques have been highlighted in this paper. There is as such not any single method which can be regarded as the best method so in this paper it is suggested that a combination of the methods should be used to get an accurate cost estimate.