| Irthlingborough to Karlovo | 1,352.18 mi (2,176.13 km) |
| Irthlingborough to Karnobat | 1,439.98 mi (2,317.42 km) |
| Irthlingborough to Kavarna | 1,462.47 mi (2,353.62 km) |
| Irthlingborough to Kazanlak | 1,376.99 mi (2,216.04 km) |
| Irthlingborough to Knezha | 1,287.09 mi (2,071.38 km) |
| Irthlingborough to Kostinbrod | 1,281.74 mi (2,062.77 km) |
| Irthlingborough to Kozloduy | 1,261.37 mi (2,029.97 km) |
| Irthlingborough to Kyustendil | 1,284.55 mi (2,067.28 km) |
| Irthlingborough to Levski | 1,334.81 mi (2,148.17 km) |
| Irthlingborough to Lom | 1,239.77 mi (1,995.21 km) |
| Irthlingborough to Lovech | 1,327.74 mi (2,136.78 km) |
| Irthlingborough to Lukovit | 1,302.98 mi (2,096.94 km) |
| Irthlingborough to Lyaskovets | 1,369.36 mi (2,203.78 km) |
| Irthlingborough to Mezdra | 1,286.51 mi (2,070.43 km) |
| Irthlingborough to Momchilgrad | 1,425.05 mi (2,293.39 km) |
