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

1. Mercury

2. Mars

3. Venus

4. Earth

5. Neptune

6. Uranus

7. Saturn

8. Jupiter

It's worth noting that this list is based on diameter, which is the measurement across a planet. If we were to order them by mass, the order would be slightly different:

1. Mercury

2. Mars

3. Venus

4. Earth

5. Uranus

6. Neptune

7. Saturn

8. Jupiter

Jupiter is the largest planet in our solar system by both diameter and mass.