Question

how fast is light's speed in km

Answer 1

299,792 kilometers per second is the answer.

Answer 2

299,792 kilometers per second

The speed of light in a vacuum is 186,282 miles per second (299,792 kilometers per second), and in theory nothing can travel faster than light. In miles per hour, light speed is, well, a lot: about 670,616,629 mph. If you could travel at the speed of light, you could go around the Earth 7.5 times in one second.