To choose a fitness mat or exercise mat, the most important thing to think about is the type of activity you plan to do on it and how frequently you train. There are three main criteria to consider: comfort, size and durability.
1. Fitting Comfort
The level of comfort you will need for your fitness mat will depend first and foremost on how frequently you train. The more often you train, the more comfort - i.e., mat thickness - you'll want.
The thickness of your mat will also depend on what kind of activities you need it for. For example, if you're doing gentle exercises such as stretching or Pilates, during which you will be barefoot and often in contact with the floor, you should opt for a soft mat that is at least 5 mm thick. It will be more comfortable and protect you from the floor.
The size of your fitness mat is also important for working out comfortably.
Obviously, you'll need to take into account how tall you are when choosing a mat, but you'll also want to consider the activities you'll be doing. If you're doing exercises where you're frequently in contact with the floor, you'll want a longer mat than if you're mostly seated or kneeling.
How frequently you train will also influence how durable to wear your mat needs to be.
If you use your fitness mat on a regular or intensive basis, choose one with a protective coating to improve its resistance to wear from sport shoes.