| Round Rock to Oerlinghausen | 5,214.61 mi (8,392.10 km) |
| Round Rock to Oestrich-Winkel | 5,260.51 mi (8,465.98 km) |
| Round Rock to Offenburg | 5,313.23 mi (8,550.81 km) |
| Round Rock to Oftersheim | 5,305.55 mi (8,538.46 km) |
| Round Rock to Ohrdruf | 5,331.89 mi (8,580.84 km) |
| Round Rock to Ohringen | 5,346.75 mi (8,604.76 km) |
| Round Rock to Olbernhau | 5,432.41 mi (8,742.61 km) |
| Round Rock to Olching | 5,453.90 mi (8,777.20 km) |
| Round Rock to Oldenburg | 5,156.34 mi (8,298.33 km) |
| Round Rock to Oldenburg in Holstein | 5,207.45 mi (8,380.58 km) |
| Round Rock to Olfen | 5,176.49 mi (8,330.76 km) |
| Round Rock to Olpe | 5,217.90 mi (8,397.40 km) |
| Round Rock to Olsberg | 5,230.07 mi (8,416.98 km) |
| Round Rock to Oranienburg | 5,346.96 mi (8,605.09 km) |
| Round Rock to Ortenberg | 5,287.37 mi (8,509.20 km) |
