How Big Is Venus? A Detailed Comparison to Earth

Venus, the second planet from the Sun, is one of the most Earth-like worlds in our solar system. Often called Earth’s twin, Venus closely matches our planet in size, mass, and density. Understanding how big Venus is helps reveal why the two planets are considered so similar—and why their environments are drastically different.

Size and Radius of Venus

Venus has a mean radius of 6,051.8 kilometers (3,760.4 miles). This makes Venus about 95% the size of Earth, which has an equatorial radius of 6,378 kilometers. Because of this small difference, Venus is nearly identical to Earth in overall shape and volume.

Mass of Venus

The mass of Venus is 4.87 × 10²⁴ kilograms, which is approximately 81.5% of Earth’s mass. Despite being slightly smaller, Venus is still massive enough to have strong surface gravity and a dense atmosphere dominated by carbon dioxide and sulfuric acid clouds.

Density and Composition

Venus has a density of 5.24 grams per cubic centimeter, very close to Earth’s density of 5.52 g/cm³. This similarity suggests that Venus has a comparable internal structure, likely consisting of a metallic core, rocky mantle, and solid crust. These Earth-like characteristics contribute to its classification as a terrestrial planet.

Surface Gravity on Venus

Because of its size and mass, the surface gravity on Venus is 0.9 g, meaning a person would weigh about 90% of their Earth weight. For example, someone who weighs 70 kg (154 lbs) on Earth would weigh roughly 63 kg (139 lbs) on Venus.

Rotation and Shape

One of the most unusual features of Venus is its extremely slow rotation. Venus takes 243 Earth days to rotate once on its axis—a rotation so slow that one Venusian day is longer than its year. Due to this slow spin, Venus maintains an almost perfectly spherical shape, unlike rapidly rotating planets such as Jupiter and Saturn, which bulge at the equator.

Why Venus and Earth Are Called Twins

Although its surface environment is harsh, with temperatures hot enough to melt lead, Venus remains Earth-like in many physical characteristics. Its similar size, mass, and density make Venus a key planet for studying planetary formation, geology, and atmospheric evolution.