Answer
The gravitational force that a planet exerts on a body located at the surface depends on the mass of the planet and of the body.
$$F= G \frac{m_{1} m_{2}}{d^{2}}$$
If Jupiter were the same size as Earth, then any object would weigh 300 times greater on Jupiter's surface than it does on Earth.
However, Jupiter's radius is 10.97 times that of Earth. Gravitational attraction also depends on the distance between the objects' centers, or in this example, the planetary radius.
This factor of distance squared in the denominator of the gravity equation weakens the force by a factor of about $11^{2} = 121$, resulting in the body only weighing about 3 times greater than it does on Earth.
