| Harpenden to Ilawa | 840.00 mi (1,351.84 km) |
| Harpenden to Imielin | 856.61 mi (1,378.59 km) |
| Harpenden to Inowroclaw | 787.03 mi (1,266.61 km) |
| Harpenden to Janow Lubelski | 983.23 mi (1,582.36 km) |
| Harpenden to Jarocin | 759.39 mi (1,222.12 km) |
| Harpenden to Jaroslaw | 1,006.63 mi (1,620.01 km) |
| Harpenden to Jasien | 801.46 mi (1,289.83 km) |
| Harpenden to Jaslo | 960.32 mi (1,545.49 km) |
| Harpenden to Jastrzebie-Zdroj | 833.00 mi (1,340.59 km) |
| Harpenden to Jawor | 713.40 mi (1,148.11 km) |
| Harpenden to Jaworzno | 857.60 mi (1,380.18 km) |
| Harpenden to Jedrzejow | 894.34 mi (1,439.31 km) |
| Harpenden to Jelcz-Laskowice | 761.98 mi (1,226.28 km) |
| Harpenden to Jelenia Gora | 695.47 mi (1,119.26 km) |
| Harpenden to Jozefoslaw | 908.00 mi (1,461.28 km) |
