| Harpenden to Smolyan | 1,371.45 mi (2,207.14 km) |
| Harpenden to Sofia | 1,268.42 mi (2,041.32 km) |
| Harpenden to Sopot | 1,327.70 mi (2,136.73 km) |
| Harpenden to Sozopol | 1,457.86 mi (2,346.19 km) |
| Harpenden to Sredets | 1,440.03 mi (2,317.50 km) |
| Harpenden to Stamboliyski | 1,340.86 mi (2,157.91 km) |
| Harpenden to Stara Zagora | 1,373.26 mi (2,210.05 km) |
| Harpenden to Svilengrad | 1,423.74 mi (2,291.28 km) |
| Harpenden to Svishtov | 1,313.07 mi (2,113.17 km) |
| Harpenden to Targovishte | 1,378.36 mi (2,218.25 km) |
| Harpenden to Teteven | 1,297.04 mi (2,087.38 km) |
| Harpenden to Troyan | 1,316.67 mi (2,118.98 km) |
| Harpenden to Tryavna | 1,349.25 mi (2,171.40 km) |
| Harpenden to Tutrakan | 1,348.90 mi (2,170.85 km) |
| Harpenden to Varna | 1,434.93 mi (2,309.29 km) |
