Abstract: The calculation of droplet shape has always been based on the Laplace equation of the liquid surface, which involves knowledge of differential geometry and is difficult for younger college students to understand. This article proposes an easy to understand method to derive the shape equations of droplets on ceilings through the isolated object method, and numerically solve their shapes; A longstanding error in international research has been discovered when determining the upper limit of the volume of suspended droplets. The current necessary conditions for the stability of pendent drop are supplemented, applying the new necessary conditions to determine the upper limit of the volume of pendent drop when the contact angle is constant, and a volume upper limit fitting formula with an accuracy of up to 10-4 is provided.

Key words:  droplet shape, surface tension, pendent drop, upper limit of mass