World Diameter (km) Gravity

1. Jupiter 142,800 2.6431
2. Saturn 120,540 1.1013
3. Uranus 51,118 0.8799
4. Neptune 49,528 1.1408
5. Earth 12,756 1.0000
6. Venus 12,104 0.9125
7. Mars 6,787 0.3821
8. Ganymede (Jupiter) 5,262 0.1542
9. Titan (Saturn) 5,150 0.1409
10. Mercury 4,878 0.3924
11. Callisto (Jupiter) 4,800 0.1206
12. Io (Jupiter) 3,630 0.1802
13. Moon (Earth) 3,467 0.1611
14. Europa (Jupiter) 3,130 0.1435
15. Triton (Neptune) 2,700 0.0607
16. Pluto 2,300 0.0534
17. Titania (Uranus) 1,580 0.0200
18. Rhea (Saturn) 1,530 0.0281
19. Oberon (Uranus) 1,520 0.0106
20. Iapetus (Saturn) 1,440 0.0225
21. Charon (Pluto) 1,190 0.0210
22. Umbriel (Uranus) 1,170 0.0083
23. Ariel (Uranus) 1,160 0.0127
24. Dione (Saturn) 1,120 0.0222
25. Tethys (Saturn) 1,050 0.0153
26. Ceres (Asteroid) 914 0.0441

Notes:
Pluto ranks 15th in size. Triton is larger.
Mercury and Callisto are about the same size.
The Moon, Io and Europa are about the same size (note surface gravity of each- Io is much denser).