You can make your thighs bigger by building muscle from leg workouts using heavy weights. Some of the most effective leg workouts to make your thighs bigger include any exercises targeting the hamstrings, inner thighs, and quads such as barbell squats, walking lunges, hip thrusts, hamstring curls, and hip abductors. You will also need to supplement your diet in order to gain weight in your thighs by eating more calories daily to put on more muscle and sustain that weight.