The Kardashev Scale measures a civilization's technological advancement by the amount of energy it can harness. Nikolai Kardashev proposed the scale in 1964 with three categories:
A planetary civilization that can harness and store all of the energy available on its home planet.
A stellar civilization that can harness the total energy of its star (e.g. capturing the Sun's output with a Dyson Sphere).
A galactic civilization that can control energy on the scale of its entire galaxy.
Carl Sagan introduced a formula-based interpolation of the original Kardashev types. Instead of the large jumps between types, energy consumption grows more continuously. Conveniently, each 0.1 step on the scale corresponds to a tenfold increase in energy usage. Under this formula, Earth's civilization rates at approximately 0.7, meaning we are partway toward Type I but not there yet. The intermediate values allow for more precise comparisons between civilizations that would otherwise all fall into the same broad category.
Other theorists have extended the scale to include higher levels of energy manipulation, but the original three types remain the most widely discussed.