Mars is about half the size of Earth, however has a much smaller surface area, of about 144.4 million kilometres squared. It also has a much smaller mass, of about 6.39 × 10^23 kg. Its circumference is however slightly more than half of Earth's, at around 21,344 km. Its density is less than Earth's by a moderate amount, at 3.93 g/cm³. All of this means that Mars' gravity is about 38% of Earth's, meaning that your weight is 38% of what it is on Earth.