How to Find Measurements, Proportions, and Angles to Draw with Pencil & Thumb Method
The only way that a beginning artist can develop the ability to see and then indicate correct proportions is to become acutely aware of proportions by observation and practice sketching. Unfortunately nobody can teach you this important phase of drawing. But you CAN estimate proportions and then check them with a fair degree of accuracy by employing what is called the thumb-and-pencil method of finding proportions.