How can you convert kilograms into meters?

Answer 1

"Kilograms measure mass (often called weight); meters measure length. Because they measure different things, you cannot compare the two."

Yes and no. The measure different things, but you can compare the two by following the two steps here:

(1) multiply by Newton's gravitational constant (G=6.67E-11 m^3/kg/s^2)

(2) divide by the speed of light squared (c^2=9E16 m^2/s^2)

You end up with 7.41E-28 m/kg as your conversion factor.

This is often done in General Relativity, outside of that arena you'll likely never see this.