| South Portland to Popovo | 4,529.19 mi (7,289.03 km) |
| South Portland to Provadia | 4,583.79 mi (7,376.89 km) |
| South Portland to Radnevo | 4,561.80 mi (7,341.51 km) |
| South Portland to Radomir | 4,430.31 mi (7,129.90 km) |
| South Portland to Rakitovo | 4,500.16 mi (7,242.30 km) |
| South Portland to Rakovski | 4,523.22 mi (7,279.42 km) |
| South Portland to Razgrad | 4,532.64 mi (7,294.59 km) |
| South Portland to Razlog | 4,479.08 mi (7,208.38 km) |
| South Portland to Ruse | 4,498.15 mi (7,239.07 km) |
| South Portland to Samokov | 4,463.85 mi (7,183.86 km) |
| South Portland to Sandanski | 4,484.62 mi (7,217.30 km) |
| South Portland to Sevlievo | 4,498.17 mi (7,239.11 km) |
| South Portland to Shumen | 4,559.76 mi (7,338.22 km) |
| South Portland to Silistra | 4,537.06 mi (7,301.69 km) |
| South Portland to Sliven | 4,561.51 mi (7,341.04 km) |
