Radio waves travel at the speed of light in a vacuum: about 299,792,458 meters per second, usually rounded to 300,000 km/s or about 186,000 miles per second.

Quick Scoop

  • In empty space (a vacuum), radio waves move at essentially the same speed as visible light, X‑rays, and all other electromagnetic waves.
  • That speed is about 300,000 kilometers per second (3 × 10⁸ m/s).
  • Through air, they are only very slightly slower, so for most everyday purposes we treat them as traveling at the full speed of light.
  • In denser materials (like glass, water, or cables), they slow down depending on the material’s properties, but the exact amount varies by medium.

A quick way to picture it

If you could flip on a giant cosmic “radio lamp,” its waves would circle the entire Earth in about 0.13 seconds—less time than a blink.

Information gathered from public forums or data available on the internet and portrayed here.