| Southborough to Karlovo | 1,290.97 mi (2,077.62 km) |
| Southborough to Karnobat | 1,381.97 mi (2,224.06 km) |
| Southborough to Kavarna | 1,408.63 mi (2,266.98 km) |
| Southborough to Kazanlak | 1,316.60 mi (2,118.86 km) |
| Southborough to Knezha | 1,227.23 mi (1,975.03 km) |
| Southborough to Kostinbrod | 1,218.56 mi (1,961.08 km) |
| Southborough to Kozloduy | 1,201.82 mi (1,934.14 km) |
| Southborough to Kyustendil | 1,219.08 mi (1,961.93 km) |
| Southborough to Levski | 1,276.15 mi (2,053.76 km) |
| Southborough to Lom | 1,179.57 mi (1,898.34 km) |
| Southborough to Lovech | 1,267.77 mi (2,040.28 km) |
| Southborough to Lukovit | 1,242.36 mi (1,999.38 km) |
| Southborough to Lyaskovets | 1,310.80 mi (2,109.53 km) |
| Southborough to Mezdra | 1,225.02 mi (1,971.48 km) |
| Southborough to Momchilgrad | 1,361.88 mi (2,191.73 km) |
