Do I need an exercise mat if I already have a yoga mat?

It depends on your workouts. Yoga mats are typically 4 6mm thick and optimized for grip during balance poses. Exercise mats are 8 15mm thick and designed to cushion joints during HIIT, ab work, and floor exercises. If you mainly do yoga and stretching, a yoga mat is fine. If you do burpees, planks, or any high impact floor work, a thicker exercise mat protects your knees and elbows significantly better.