Fitness is often measured in four areas: aerobic fitness, muscular strength and endurance, flexibility, and body composition. You'll need a stopwatch or a watch that can measure seconds to complete your evaluation. A measuring tape made of fabric or plastic is useful for measuring your flexibility. There are several ways to evaluate your fitness level. The most common method is to use a "fitness test" which gives you a score that indicates how fit you are. These tests include walking or running laps, using stairs up or down, and answering questions about your health history which may influence what kind of tests you should have done as part of your evaluation. Another way to evaluate your fitness is by looking at your heart rate while you're exercising. If you wear a heart-rate monitor like a chest belt or wrist band, then you've got an accurate way to know how hard you're working out and how much energy you're burning. A final way to assess your fitness is by looking at your weight loss if you're trying to lose fat or maintain your current weight. The more muscle you have, the more calories you burn even when sitting on idle equipment, so overweight people who want to lose weight should focus on building muscle mass instead of only losing fat. You can also use fitness tests to track your progress over time.