How Long Is a Day on Venus? Longer Than Its Year

How long is a day on Venus? Longer than its year. That sounds wrong, but it's true. Venus takes about 243 Earth days to spin once on its axis. It needs only about 225 Earth days to circle the Sun. On top of that, it spins backward, so the Sun rises in the west. And it gets stranger: the time from one sunrise to the next is a different number again. We'll show you how it all fits together and which planet has the longest day of all.

How long is a day on Venus?

One full rotation of Venus takes about 243 Earth days. One Venus year, a trip around the Sun, takes only about 225 Earth days. So Venus spins more slowly than it orbits. The time from one sunrise to the next is about 117 Earth days.

Why two numbers for one day? Because there are two ways to measure a day. The first counts how long the planet takes to turn all the way around. For Venus, that's 243 Earth days. The second counts how long the Sun takes to return to the same spot in the sky. That's the day you would actually live through there.

On Earth, both numbers are almost the same: 24 hours. On Venus, they are far apart. The reason is the spin direction, because Venus turns against its own orbit. That brings the Sun back to its starting point sooner. One solar day on Venus lasts almost four Earth months.

Why does the Sun rise in the west on Venus?

Venus spins backward. Scientists call this retrograde rotation. Most planets spin the way Earth does, from west to east. Venus spins from east to west. Its axis is tilted almost upside down, by about 177 degrees.

For you, that would mean the Sun rising in the west and setting in the east. You wouldn't see it, though. Venus is wrapped in thick clouds. And the ground is about 465 °C (870 °F), hot enough to melt lead. Read more in our post Which Planet Is the Hottest in the Solar System?.

How fast does Venus spin compared to Earth?

Venus is almost the size of Earth. Its diameter is about 12,100 km (7,500 mi), and Earth's is about 12,750 km (7,900 mi). Still, it spins far more slowly. Quick math: the distance around Venus at the equator is about 38,000 km. A spot on the ground needs 243 Earth days to cover it. That works out to about 6.5 km/h.

A brisk walker manages about 3 mph. You could almost outwalk the ground of Venus. How fast our own planet spins, and why you don't feel it, is the topic of How Fast Does the Earth Spin, Really?.

Want to see how well you can guess numbers like these? Try our science estimation questions. Free, runs in your browser, and perfect for your next road trip.

Does Venus have the longest day in the solar system?

Here's where it gets interesting: it depends on how you measure. For pure rotation, Venus wins by a mile. At 243 Earth days, it spins more slowly than any other planet. Mercury needs about 59 Earth days for one turn. All the other planets turn in a few hours.

For the sunrise-to-sunrise day, though, Mercury wins. About 176 Earth days pass between two sunrises there. That is twice as long as a Mercury year, which lasts only about 88 Earth days. So on Mercury, a solar day is longer than a year. On Venus, that's only true for the pure rotation.

Why does Venus spin so slowly and backward?

There is no sure answer yet. The cause is not settled, and researchers discuss several explanations. What we know for certain is the result: Venus is a planet that almost stands still while running backward.

Facts like this are why estimation questions are so much fun. Most people guess a Venus day of about 24 hours, because Venus is similar in size to Earth. Reality is off by almost 6,000 hours.

Frequently asked questions about a day on Venus

The takeaway in one sentence

A day on Venus is longer than its year if you count pure rotation, and the Sun rises in the west there. If you like surprises like this, jump into our science questions or browse the homepage for more estimation questions.