Leaf area is a key variable in the study of physiology, horticulture and crop science It is major parameter in plant modelling studies, to develop physiological model in plant breeding. The plant Putranjiva roxburghii and Morinda citrifolia L.(Medicinal plants) were selected and the leaves of these plants were used for development of linear model for leaf area using Counting grid method. Leaf samples were randomly selected from the lower, middle and upper parts of the plant with different sizes of Leaves. Length, width, L², W², product of these dimensions and leaf fresh and dry weights and their water content of 25 leaf samples were assessed and compared with actual leaf area measured by graph tracing method, to test their accuracy and reliability using Y= a + bX model. The validation of the models indicates that model (LA = a + bL_W) was accurate and reliable to determine the leaf area of both plant and therefore would be very useful for field workers dealing with large samples.And the development of linear models for Putranjiva roxburghii and Morinda citrifolia L. is first reported in Gujarat during this study.