Simple Forms

The arm can be simplified down to three spheres for the joints (shoulder, elbow, and wrist) and two cylinders for the arm bones themselves. In these examples, I have added in the hand, if you are only focused on drawing the arm I recommend just placing a box for the hand so that you start to visualize the relationship between the arm and hand. 

If you are just getting into drawing, cylinders can be quite tricky, I have a tutorial on the basic forms that you can check out here (Opens in a new window). This method of drawing depends heavily on these basic forms which can be frustrating at first but it makes everything easier in the long haul.

Practice from references by copying the pose of the arm but simplifying down the shapes to our basic forms. Do this until you are comfortable with the overall proportions of the arm.

Complex Forms

Drawing in the arm muscles is fairly simple once you have developed an understanding of the cylinders (especially when drawing skinny arms). The biggest challenge during this step is drawing in the shoulder, pay close attention to how the shoulder muscle wraps around the top sphere.

For the forearm, draw the cylinder slightly thicker towards the elbow and more tapered close to the wrist. You can see that on the example drawings that there is only a slight difference here, you can exaggerate these differences if you are drawing someone muscular.

Now draw some arms in your sketchbook from reference and then some from imagination, switching back and forth will help you memorize these forms and allow you to draw accurately from imagination. 

If you want more worksheets for drawing anatomy I have a printable workbook on the basics of drawing the figure and also the hand that you can check out below~