Since most images and videos of spacecrafts are on dark, space-y backgrounds, often with only distant planets or stars to compare them to, it's pretty hard to tell how big or small they really are.
Juno that crashed into Jupiter is the size of a basketball court, New Horizons that flew by Pluto is about the size and shape of a grand piano, and the new class of GPS satellites are about the size of three bowling lanes!
The size of a spacecraft depends on a lot of things. Will it be carrying people? What is it built to do? What equipment is necessary for the environment it'll be going to?
The International Space Station is the largest spacecraft that has ever orbited planet Earth and it is huge. We're talkin' football field huge! From one end to the other, the ISS measures 357 feet. One of the main purposes of the space station is to put humans in space. So, obviously, it needs to be big enough for humans to float around in (plus scientific experiments). The ISS's livable space is as big as a six-bedroom house!