Light travel time converter
Convert a distance into the time light takes to cross it, or a light-time into kilometers, miles and AU.
That's about the same as the Sun.
What it means
How far is that?
Light in vacuum: 299,792.458 km/s, exact by definition. Planet distances change with orbits; references are typical.
Every unit
That distance in every unit
Learn
Three things worth knowing
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300,000 km a second
A light-second ≈ 300,000 km, a light-minute ≈ 18 million km, a light-hour ≈ 1.08 billion km.
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Rømer’s moons
Ole Rømer noticed in 1676 that Jupiter’s moons ran late when Jupiter was far away, and estimated the speed of light.
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A light-year is a distance
Light-seconds and light-years measure distance, not time.
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Background
About light-time
Light covers 299,792 km every second. The Moon is 1.3 light-seconds away, so radio talk with Apollo had a 2.6 s round trip; the Sun is 8.3 light-minutes away, so we see it as it was 8 minutes ago.
Mars is 3 to 22 light-minutes away, which is why rovers drive themselves.