Weight & gravity
Weight on planet = Earth weight × (planet's surface gravity ÷ Earth's gravity)
Your mass never changes — only your weight does, because weight = mass × gravity. Relative to Earth (1.00): the Moon is 0.17, Mars 0.38, Jupiter 2.53. So a 70 kg person "weighs" like ~12 kg on the Moon but ~177 kg at Jupiter's cloud tops.
Same you, different gravity
Your mass never changes, but your weight — the force of gravity on that mass — depends on where you stand. Each planet and moon has its own surface gravity, so you'd feel featherlight on the Moon (about 1/6 of Earth) and crushingly heavy on the Sun's surface (about 27×). Enter your weight to see the whole tour.