| Boulder to Popovo | 5,930.74 mi (9,544.61 km) |
| Boulder to Provadia | 5,974.60 mi (9,615.19 km) |
| Boulder to Radnevo | 5,981.28 mi (9,625.93 km) |
| Boulder to Radomir | 5,877.46 mi (9,458.85 km) |
| Boulder to Rakitovo | 5,943.51 mi (9,565.16 km) |
| Boulder to Rakovski | 5,953.16 mi (9,580.68 km) |
| Boulder to Razgrad | 5,928.53 mi (9,541.05 km) |
| Boulder to Razlog | 5,930.16 mi (9,543.67 km) |
| Boulder to Ruse | 5,895.98 mi (9,488.66 km) |
| Boulder to Samokov | 5,907.77 mi (9,507.64 km) |
| Boulder to Sandanski | 5,941.88 mi (9,562.53 km) |
| Boulder to Sevlievo | 5,916.27 mi (9,521.31 km) |
| Boulder to Shumen | 5,954.65 mi (9,583.08 km) |
| Boulder to Silistra | 5,916.48 mi (9,521.66 km) |
| Boulder to Sliven | 5,971.35 mi (9,609.96 km) |
