Common shapes in fire include teardrops and tendrils[1] X Research source for the flames and an elliptical shape for the entire space taken up by the fire.
Start to draw or paint in the shape of a fire. It’s good to use a reference for the shape, such as drawing an ellipse within which the fire will remain and you can send the flames up to any of the edges of this ellipse. [3] X Research source Use “S” like shapes to form each flame. Join the flames together about a third of the way or midway from the base of the fire and have the flames separated going up from that point. Be sure to vary the height of different flames – no flames remain the same height at the same time and the difference in height gives a greater sense of movement. See How to draw flames for some clear pointers with step-by-step images.
Fancy flames for an more abstract, funky look. Introducing a subject into the picture. A larger fire. Introducing a character with the fire. Rainbow fire.