an instrument that measures and gives a visual display of the amount, level, or contents of something

a fuel gauge

the thickness, size, or capacity of something, especially as a standard measure

the position of a sailing ship to windward (the weather gage) or leeward (the lee gage) of another

the French fleet was heavily outnumbered but had the weather gage

estimate or determine the amount, level, or volume of

astronomers can gauge the star's intrinsic brightness

measure the dimensions of (an object) with a gauge

when dry, the assemblies can be gauged exactly and planed to width