Planet Distance Calculator & Travel Time Calculator | PlanetPath

Planet Path Calculator

Planet Distance & Travel Time Calculator

Choose a planet to see how far it is from Earth in kilometers, miles and astronomical units, then enter a spacecraft speed to estimate how long the journey would take. Every calculation runs in your browser.

Plan your journey

Three steps. Your result appears as soon as a speed is entered.

Choose a destination planet

Starting point: Earth

Choose which distance to use

Set the spacecraft speed
Quick presets

For reference, Voyager 1 travels at about 61,000 km/h.

Your journey will appear here

Pick a planet and enter a speed, or tap one of the presets. The result appears instantly.

Planet profile

Mars

Approximate reference values from NASA planetary fact sheets. Moon counts are confirmed moons as of mid-2026 and change as new discoveries are confirmed.

How We Calculate Travel Time

Travel time is estimated by dividing the selected reference distance by the spacecraft speed. The result is converted from hours into days, months (30.44 days) and years (365.25 days).

The distance comes from a simplified orbital model built on NASA JPL’s approximate orbital elements for the planets. Average, Closest and Farthest are measured from that model over 1900 to 2050. On a date calculates where Earth and the planet are on the day you choose.

Real missions may take longer because spacecraft do not travel in a straight line at constant speed:

  • Orbital mechanicsSpacecraft follow curved paths around the Sun, not straight lines.
  • Acceleration and decelerationSpeed changes throughout a trip, and arriving often means slowing down.
  • Launch windowsMissions wait for the planets to line up efficiently, sometimes for years.
  • Gravity assistsFlybys of other planets save fuel but add distance and time.
Travel time=Distance÷Speed
1 mile
1.609344 km
1 astronomical unit (AU)
149,597,870.7 km
1 km/s
3,600 km/h
Speed of light
299,792.458 km/s
1 month (average)
30.44 days
1 year
365.25 days

How planetary distances work

Earth and every other planet travel around the Sun at different speeds and on slightly oval orbits. That means the distance between Earth and any planet is always changing. When two planets are on the same side of the Sun they can be relatively close; when they are on opposite sides, the Sun sits between them and the gap is enormous.

Mars shows this clearly. At its closest in recent history, in August 2003, it came within about 56 million km of Earth. When it is on the far side of the Sun it is more than 400 million km away, over seven times farther. That is why this calculator never presents one fixed number as “the” distance. Instead you can choose the average, the closest, the farthest, or the calculated distance on a specific date.

A surprising result of averaging over time: Mercury, not Venus, is the planet closest to Earth on average. Venus gets nearer at its closest approach, but it also swings far away on the other side of the Sun, while Mercury always stays close to the Sun.

Distances from Earth measured with PlanetPath’s orbital model, 1900 to 2050. Rounded to the nearest 0.1 million km.
PlanetClosestAverageFarthestAverage (AU)

How spacecraft travel time is estimated

The calculator uses the simplest possible physics: a spacecraft leaves Earth and flies straight to the planet at a constant speed. Travel time is the distance divided by that speed. It is a clear way to compare destinations and speeds, and to get a feel for the scale of the solar system.

Worked example: Earth to Mars

At the average distance of about 255 million km and a speed of 50,000 km/h, the trip takes 255,000,000 ÷ 50,000 = 5,100 hours. Dividing by 24 gives about 213 days, or roughly 7 months. At Mars’s closest approach, the same spacecraft would need only about 46 days.

Choosing a realistic speed

Useful reference points: New Horizons left Earth at about 58,500 km/h, Voyager 1 now travels at roughly 61,000 km/h, and NASA’s Parker Solar Probe has reached about 690,000 km/h close to the Sun. Our 20,000 to 200,000 km/h presets cover everything from a slow cruise to far faster than today’s typical interplanetary missions.

Why actual mission durations differ

Real spacecraft cannot point at a planet and fly straight there. They coast along curved orbits around the Sun, and they need the destination to arrive at the right place at the right time. To save fuel, many missions borrow speed from other planets through gravity assists, which adds distance but makes the trip possible. Missions that must enter orbit also need to slow down on arrival, which can take extra loops or flybys.

The table below shows how long some real missions took. Notice that Mercury, one of the closest planets, took far longer than Mars: a spacecraft falling toward the Sun speeds up, and shedding that speed is hard.

Launch to arrival (orbit insertion, landing or flyby). Durations rounded.
MissionDestinationLaunchedArrivedDuration
Venus ExpressVenus (orbit)Nov 2005Apr 2006≈ 5 months
PerseveranceMars (landing)Jul 2020Feb 2021≈ 7 months
JunoJupiter (orbit)Aug 2011Jul 2016≈ 5 years
MESSENGERMercury (orbit)Aug 2004Mar 2011≈ 6.6 years
CassiniSaturn (orbit)Oct 1997Jul 2004≈ 6.7 years
Voyager 2Uranus (flyby)Aug 1977Jan 1986≈ 8.4 years
Voyager 2Neptune (flyby)Aug 1977Aug 1989≈ 12 years

Frequently asked questions

How far is each planet from Earth right now?

Choose the “On a date” distance option. It uses today’s date by default and calculates the positions of Earth and the selected planet with NASA JPL’s approximate orbital elements, which are valid from 1800 to 2050.

What does “average distance” mean in this calculator?

It is the time-averaged distance between Earth and the planet from 1900 to 2050, sampled twice a day with an orbital model. For Mars this is about 255 million km. You may also see about 225 million km quoted elsewhere; that figure uses a different definition, roughly the midpoint of the closest and farthest distances.

Which planet is closest to Earth?

Venus comes closest, at about 40 million km. Averaged over time, though, Mercury is the nearest planet to Earth, at about 155 million km, because it never strays far from the Sun.

How accurate are the calculator’s results?

The distances are close to real values; for example, the model gives about 96.1 million km for Mars’s closest approach on 12 January 2025. The travel times are simplified estimates that assume a straight line at constant speed, so they are for education and comparison rather than mission planning.

Why does it take years to reach Mercury if it is so close?

A spacecraft falling toward the Sun speeds up, so reaching Mercury means shedding a lot of speed. NASA’s MESSENGER needed six planetary flybys and about 6.6 years before it could enter orbit around Mercury in 2011.

How fast do real spacecraft travel?

New Horizons left Earth at about 58,500 km/h, and Voyager 1 now travels at roughly 61,000 km/h. NASA’s Parker Solar Probe has reached about 690,000 km/h near the Sun, the fastest speed of any human-made object.

How long would it take to reach Mars at the speed of light?

Light takes about 3 minutes at Mars’s closest approach, about 14 minutes at the average distance, and about 22 minutes when Mars is farthest away.

Can I share my result?

Yes. Select Copy Result to copy a clean text summary with a link that reopens the calculator with the same planet, distance option and speed.