| Mercer Island to Smolyan | 5,953.34 mi (9,580.98 km) |
| Mercer Island to Sofia | 5,855.46 mi (9,423.45 km) |
| Mercer Island to Sopot | 5,885.79 mi (9,472.26 km) |
| Mercer Island to Sozopol | 5,954.02 mi (9,582.07 km) |
| Mercer Island to Sredets | 5,949.64 mi (9,575.02 km) |
| Mercer Island to Stamboliyski | 5,914.86 mi (9,519.05 km) |
| Mercer Island to Stara Zagora | 5,916.42 mi (9,521.56 km) |
| Mercer Island to Svilengrad | 5,969.51 mi (9,607.00 km) |
| Mercer Island to Svishtov | 5,834.71 mi (9,390.06 km) |
| Mercer Island to Targovishte | 5,880.47 mi (9,463.70 km) |
| Mercer Island to Teteven | 5,859.57 mi (9,430.07 km) |
| Mercer Island to Troyan | 5,870.18 mi (9,447.14 km) |
| Mercer Island to Tryavna | 5,885.73 mi (9,472.17 km) |
| Mercer Island to Tutrakan | 5,829.29 mi (9,381.34 km) |
| Mercer Island to Varna | 5,905.71 mi (9,504.32 km) |
