Here are the planets in our solar system ordered from smallest to largest diameter:

1. Mercury: 4,880 km (3,032 miles)

2. Mars: 6,779 km (4,217 miles)

3. Venus: 12,104 km (7,521 miles)

4. Earth: 12,742 km (7,926 miles)

5. Neptune: 49,528 km (30,775 miles)

6. Uranus: 51,118 km (31,763 miles)

7. Saturn: 120,536 km (74,898 miles)

8. Jupiter: 142,984 km (88,846 miles)

It's important to note that this list only considers the diameter of the planets themselves. If we were to include the diameters of the planets' rings, Saturn would be significantly larger.