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Mercury's Size

Mercury is the second smallest planet; only Pluto is smaller. Mercury’s diameter is 4879 km, while Earth’s is 12,756 km. In fact, Mercury is not much larger than our Moon, which has a diameter of 3475 km.

day on mercury animation

How do the planets size up? Check out the "Planet Size Comparison" animation. Click on the image above.

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The Sun’s diameter is 1.38 x 106 km, making it about 286 times larger than Mercury. So if you were to make a scale model of Mercury and the Sun, representing Mercury by a marble 1.0 cm across, the sphere representing the Sun would be 2.86 m in diameter!