What is gravity in space compared to earth?

Earth's surface value, 9.80 m/s², is the benchmark everything else is measured against. At the altitude where the International Space Station flies, about 400 km (250 mi), the pull has fallen only to roughly 90% of that, because the station is barely 6% farther from the planet's centre than the launch pad. Stand on the Moon and you feel 1.62 m/s², close to one sixth. On Mars it is 3.71 m/s², a little over a third. Between the stars gravity becomes vanishingly small, but it never actually reaches zero.

Since the crews are weightless, the natural assumption is that gravity up there is near nothing. In fact they would weigh almost as much as on Earth if they could stand on a fixed platform at that height. They float because they and their vehicle are falling around the planet together, at the same rate, with nothing to press against. The term microgravity refers to the tiny residual accelerations left over from vibration, atmospheric drag and manoeuvres — not to a weak gravitational field.

Surface gravity follows from a body's mass and radius together, so a small dense world can out-pull a larger, lighter one. The consequences are practical and large: a lunar lander needs a fraction of the thrust an Earth launch demands to raise the same mass, Apollo crews adopted a loping gait because a normal stride sent them airborne, and Martian gravity is strong enough for dust to settle and liquids to pour normally yet probably too weak to protect bone and muscle over a stay measured in years. Structural design, spacesuit mass, the behaviour of a flame and even how a wrench feels in the hand all shift with the local value.