How high must one be above the Earth's surface to experience zero gravity, i.e., at what altitude could a person float around in a spacecraft without effort?

I'm pondering the concept of Newton's inverse-square law of universal gravitation...

(At an altitude of 200 miles, according to Newton's inverse-square law of universal gravitation, gravity is just 10% weaker than it is at the Earth's surface. "Weightlessness" and "zero gravity" describe an astronaut's sensation in orbit, but the conditions under which an astronaut floats about within a spacecraft would be better described as free fall.)

http://ataridogdaze.com/weightless/outer-space.shtml

Less than six miles according to https://www.quora.com/At-what-altitude-does-the-Earths-gravity-no-longer-have-an-effect-on-the-astronauts-or-the-space-shuttle which has it as between approximately 24,000 and 32,000 feet altitude.

nb updated link explains our gravity tends to zero so becomes minuscule but present nonetheless, see first diagram. (satguru)