How fast does light travel, in kilometres per second?
Science medium Data from 2024
Guess before you scroll — the answer is below
The answer
299,792 kilometres per second
Roughly 299.8K.
Light travels at 299,792 km per second — fast enough to circle the Earth seven and a half times in one second. Since 1983 the metre has been *defined* by this speed, so it is exact by definition rather than measured.
Where this number comes from
| Source | International Bureau of Weights and Measures (BIPM) |
|---|---|
| Figure refers to | 2024 |
| Last checked | |
| Unit | kilometres per second |
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