What is the approximate equatorial diameter of Venus in kilometers?

Venus has an approximate equatorial diameter of 12,104 kilometers. That makes it only about 638 kilometers smaller across than Earth, whose equatorial diameter is roughly 12,756 kilometers.

Venus is often called Earth's sister planet because the two worlds are similar in size, mass, and rocky composition. However, Venus is almost perfectly spherical because its extremely slow rotation produces very little equatorial bulging. Earth, spinning once every 24 hours, is noticeably wider at its equator than from pole to pole.

The similar size does not mean similar conditions. Venus is wrapped in a dense carbon-dioxide atmosphere, has crushing surface pressure, and reaches temperatures hot enough to melt lead. Its cloud-covered surface was mapped mainly with radar by spacecraft such as NASA's Magellan mission, because visible light cannot penetrate the planet's thick clouds.

A common mix-up is confusing Venus's diameter with its radius. Venus's radius is about 6,052 kilometers, so its diameter is approximately twice that figure. The planet's orbital size is also a different measurement: Venus travels around the Sun at an average distance of about 108 million kilometers.