It's tricky to say exactly how big Earth's orbit is because it's not a perfect circle, but rather an ellipse. Here are the key measurements:

* Semi-major axis: This is the average distance between Earth and the Sun, which is about 149.6 million kilometers (93 million miles).

* Perihelion: This is the closest Earth gets to the Sun, which is about 147.1 million kilometers (91.4 million miles).

* Aphelion: This is the furthest Earth gets from the Sun, which is about 152.1 million kilometers (94.5 million miles).

So, you could say Earth's orbit is approximately 150 million kilometers (93 million miles) in radius, but remember that it varies slightly throughout the year.