The Moon is about 384,400 km (238,855 miles) from Earth on average. Because its orbit is an oval, the distance changes from about 356,500 km at its closest to about 406,700 km at its farthest. Light takes about 1.28 seconds to make the trip one way. Scientists measure this distance to within about a millimetre by firing lasers at mirrors left on the Moon, a technique called lunar laser ranging.
This guide gives the distance, explains how the measurement works, and covers what it has taught us, including the fact that the Moon is slowly drifting away from us.
How far away is the Moon?
| Distance (km) | Distance (miles) | Light travel time, one way | |
|---|---|---|---|
| Closest (perigee) | About 356,500 | About 221,500 | About 1.19 seconds |
| Average | About 384,400 | About 238,855 | About 1.28 seconds |
| Farthest (apogee) | About 406,700 | About 252,700 | About 1.36 seconds |
The distance varies by roughly 50,000 km during each orbit. When a full Moon happens near the closest point, it appears bigger and brighter and is often called a supermoon.
To get a feel for the size of that gap:
- A car at 100 km/h would take about 160 days, driving non-stop.
- A passenger jet at 900 km/h would take about 18 days.
- The Apollo astronauts took about three days.
- Light takes about 1.3 seconds.
The Moon is the only natural moon of Earth. For how it compares with other planets, see our guide to how many moons each planet has.
Try it yourself
The widget below has three parts. Fire a laser pulse in real time and watch how long the round trip takes, see how far the Moon drifts over time, and find the five reflector sites on the lunar surface.
Measuring the Moon with a laser
Fire a pulse, change the distance, and find the mirrors astronauts left behind.
1. Time a laser pulse to the Moon and back
2. The Moon is drifting away
3. Mirrors on the lunar surface
Distances use the Moon’s approximate closest and farthest points. The 3.8 cm per year drift is the average rate measured by laser ranging, and it has changed over geological time. Sources: NASA and the International Laser Ranging Service.
How do scientists measure the distance to the Moon?
The method is simple in principle. A telescope sends a very short pulse of laser light toward the Moon. A mirror there reflects it back. A detector on Earth records exactly how long the round trip took. Because the speed of light is known very precisely, the distance is the speed of light multiplied by the round-trip time, divided by two.
Before lasers, astronomers used other methods:
- Parallax: Observers in different places on Earth measured the Moon’s position against the stars and used geometry to find the distance.
- Radar: In 1946, the US Army Signal Corps bounced radar waves off the Moon for the first time.
- Early lasers: In 1962, a team at MIT detected laser light reflected from the Moon’s rough surface.
The breakthrough for precision came in 1969, when Apollo 11 astronauts placed a special mirror on the Moon.
What are the Apollo retroreflectors?
A retroreflector is a set of mirrors arranged so that light bouncing off them goes straight back toward where it came from, no matter what angle it arrives at. The Moon reflectors use “corner cubes”, which work like the inside corner of a box.
Five reflector sites are in regular use:
- Apollo 11 (1969): 100 corner cubes.
- Apollo 14 (1971): 100 corner cubes.
- Apollo 15 (1971): 300 corner cubes, the largest and most-used array.
- Lunokhod 1 (1970): A French-built reflector on a Soviet rover.
- Lunokhod 2 (1973): A reflector on a second Soviet rover.
Lunokhod 1 has an unusual story. Contact with the rover was lost, and its exact position was unknown for decades. In 2010, NASA’s Lunar Reconnaissance Orbiter photographed it, and scientists were able to range to it again.
More reflectors have been added recently. In late 2023, the laser altimeter on NASA’s Lunar Reconnaissance Orbiter detected a small reflector carried by India’s Chandrayaan-3 lander. Scientists have also proposed new designs with a single large cube that could improve accuracy further.
Why is lunar laser ranging so difficult?
It takes extreme precision for three reasons.
The beam spreads out. Even a very narrow laser beam is several kilometres wide by the time it reaches the Moon. The returning light spreads out again on the way back.
Very few photons return. Each pulse contains a huge number of photons, but only a handful make it back to the telescope, and many pulses return none at all. Observatories have to fire thousands of pulses and filter out the sunlight and background noise.
The timing must be exact. To measure distance to a millimetre, the timing has to be accurate to a few picoseconds, which is trillionths of a second.
Because of these challenges, only a small number of observatories around the world can do it, including stations in France, Italy, Germany and the United States. They coordinate through the International Laser Ranging Service.
What has lunar laser ranging taught us?
Fifty years of measurements have produced some of the most precise tests in space science.
The Moon is moving away. The distance is growing by about 3.8 cm a year, about as fast as a fingernail grows. The cause is tides. Earth’s gravity raises tidal bulges in the oceans, and Earth’s spin drags them slightly ahead of the Moon. The bulges pull the Moon forward, which raises its orbit, while Earth’s rotation slows down in return. Our days are getting longer by roughly two milliseconds per century.
This also means that, in several hundred million years, the Moon will be too far away to cover the Sun completely, and total solar eclipses will stop.
Einstein’s theory holds up. Laser ranging tests whether Earth and the Moon fall toward the Sun at the same rate, a key prediction of general relativity. They do, to within about one part in ten trillion. Learn more about the theory in our guide to general relativity and spacetime and in the space physics and relativity section.
Gravity appears steady. The measurements show no sign that the gravitational constant is changing over time, within very tight limits.
The Moon’s inside is not solid. Small wobbles in how the Moon rotates reveal that it has a molten or partly molten core.
Did China fire a laser at the Moon in daylight?
Not exactly, and it is worth getting right. On 26 and 27 April 2025, a team from China’s Deep Space Exploration Laboratory and the Yunnan Observatories fired near-infrared laser pulses from a 1.2-metre telescope at the Tiandu-1 satellite, and detected the reflected light from a retroreflector on the spacecraft.
Tiandu-1 was about 130,000 km from Earth, roughly a third of the way to the Moon. Tiandu-1 was launched in March 2024 to test communication and navigation technology around the Moon. The achievement was described as the first successful satellite laser ranging in Earth–Moon space during strong daylight. Daylight is hard because sunlight drowns out the faint returning signal.
It was not a laser shot at the lunar surface, and it was not a weapon test. The practical goal is to track spacecraft near the Moon more often, because measurements no longer have to wait for the night. That will help with navigation as more missions head to the Moon, including those planned under NASA’s Artemis programme. See Artemis pictures from space for the latest views.
Can you see the Apollo reflectors?
No. The reflectors are only a few tens of centimetres across and cannot be seen from Earth, even with large telescopes. NASA’s Lunar Reconnaissance Orbiter has photographed the Apollo landing sites from lunar orbit, showing equipment and the tracks left by the astronauts. To read more about the missions themselves, see our space exploration history section.
Frequently asked questions
How far is the Moon from Earth in miles?
About 238,855 miles on average. It ranges from roughly 221,500 miles at its closest to 252,700 miles at its farthest.
How long does light take to reach the Moon?
About 1.28 seconds on average. A laser pulse goes there and back in about 2.56 seconds.
How do scientists measure the distance to the Moon?
They fire short laser pulses at mirrors left on the lunar surface, time the round trip, and calculate the distance from the speed of light.
Who put the mirrors on the Moon?
Apollo 11, 14 and 15 astronauts placed three of them, and Soviet Lunokhod rovers carried two more.
Is the Moon moving away from Earth?
Yes, by about 3.8 cm a year. Tidal forces between Earth and the Moon are responsible.
Why does the Moon’s distance change?
Its orbit is an oval, not a circle, so it moves closer and farther away during each orbit.
Can I bounce a laser pointer off the Moon?
A small laser cannot be detected from a backyard, because the returning light is far too faint without a large telescope and special detectors. Never point a laser at aircraft or people.
Key takeaways
- The Moon is 384,400 km away on average, ranging from about 356,500 to 406,700 km.
- Light takes about 1.28 seconds to reach it.
- Lunar laser ranging uses mirrors left by Apollo astronauts and Soviet rovers to measure distance to about a millimetre.
- The Moon is drifting away at about 3.8 cm a year because of tides.
- China’s 2025 daylight test ranged to the Tiandu-1 satellite, not the Moon itself.
Continue exploring in our Solar System guide.