You can tell if a lawn has too much grass or too many weeds by observing its appearance and growth patterns. If the lawn is thick, lush, and uniform in color and texture, it likely has a healthy amount of grass. If it has bare patches, thin or yellowing grass, and uneven growth, it may have too few grasses or too many weeds. Weeds can be identified by their different shapes, colors, and growth habits compared to grasses. A professional lawn care expert can also provide an assessment and recommend solutions.