Evaporation is a common phenomenon in everyday life. However, most previous studies have focused on the evaporation of a small sessile drop, and a systematic approach to the evaporation rate of a large drop is insufficient. The shape of a drop is determined by the relative effect of gravity and surface tension, and the two relative forces are represented by the dimensionless number Bo. Previous studies noted that when a small droplet evaporates, diffusion dominates and the evaporation rate is proportional to the radius of the droplet. On the contrary, for the large drop evaporation, convection dominates and the evaporation rate is proportional to the square of the radius of the drop. In this paper, the profile of a water drop on a solid substrate, changing from a puddle to a small droplet is calculated by solving the Young-Laplace equation and related ordinary differential equations (ODEs) through Mathematica. We also provide the water drop evaporation experiment data done on a scale to track the evaporation rate, and the shape of the drop monitored by a video camera. We compare the calculated data and the experimental data and conclude that for the evaporation of a puddle with an extremely small contact angle, the evaporation rate is proportional to the radius of the drop not to the square of the radius of the drop.