| Porsgrunn to Olympia Heights (Florida) | 4,709.05 mi (7,578.48 km) |
| Porsgrunn to Omaha (Nebraska) | 4,320.88 mi (6,953.78 km) |
| Porsgrunn to On Top of the World Designated Place (Florida) | 4,581.41 mi (7,373.07 km) |
| Porsgrunn to Onalaska (Wisconsin) | 4,030.85 mi (6,487.02 km) |
| Porsgrunn to Oneida (New York) | 3,589.20 mi (5,776.27 km) |
| Porsgrunn to Oneonta (New York) | 3,602.31 mi (5,797.36 km) |
| Porsgrunn to Ontario (California) | 5,330.00 mi (8,577.81 km) |
| Porsgrunn to Ontario (Oregon) | 4,692.66 mi (7,552.10 km) |
| Porsgrunn to Opa-locka (Florida) | 4,696.06 mi (7,557.57 km) |
| Porsgrunn to Opelika (Alabama) | 4,481.39 mi (7,212.11 km) |
| Porsgrunn to Opelousas (Louisiana) | 4,821.70 mi (7,759.77 km) |
| Porsgrunn to Orange (California) | 5,349.95 mi (8,609.91 km) |
| Porsgrunn to Orange (Texas) | 4,898.51 mi (7,883.40 km) |
| Porsgrunn to Orange City (Florida) | 4,557.34 mi (7,334.33 km) |
| Porsgrunn to Orangeburg (South Carolina) | 4,284.67 mi (6,895.52 km) |
