The transient shape and volume of evaporating sessile droplets are critical to our understanding and prediction of deposits left over on the solid surface after droplet evaporation. The 2/3 power law of scaling, (V/V-o)(beta) = 1 t/t(f) with beta = 2/3, has been widely used. The 1/1 power law of scaling with beta = 1 was also obtained for vanishingly small contact angles. Here we show that beta significantly deviates from 2/3 and 1 when the droplet base is pinned: beta depends on both initial and transient contact angles. The 1/1 power law presents the upper limit of beta = 1, while beta = 2/3 is the lower limit if contact angles are smaller than 148 degrees. Unexpectedly, beta can be smaller than 2/3 if contact angles are larger than 148 degrees. We also present a semianalytical approximation for beta as a function of the initial contact angle.