The height of your mattress matters for two reasons:
Mattress thickness contributes to the overall height of your bed, which is essential for the sleeper’s comfort and health.
A thinner mattress won’t provide enough support for the sleeper.
A mattress should be at least 8 inches thick so it can support your body and help keep you in a neutral position (a neutral position is when your neck, spine, and hips are aligned and your weight is evenly distributed). However, many find 12 inch mattresses provide the pinnacle of comfort.