| Helensburgh to Mangualde | 1,073.68 mi (1,727.93 km) |
| Helensburgh to Marco de Canavezes | 1,036.38 mi (1,667.89 km) |
| Helensburgh to Marinha Grande | 1,140.11 mi (1,834.83 km) |
| Helensburgh to Massama | 1,210.66 mi (1,948.37 km) |
| Helensburgh to Matosinhos | 1,040.35 mi (1,674.28 km) |
| Helensburgh to Mealhada | 1,093.23 mi (1,759.39 km) |
| Helensburgh to Melgaco | 973.29 mi (1,566.36 km) |
| Helensburgh to Melres | 1,046.09 mi (1,683.53 km) |
| Helensburgh to Mira | 1,091.87 mi (1,757.19 km) |
| Helensburgh to Miranda do Corvo | 1,111.84 mi (1,789.34 km) |
| Helensburgh to Mirandela | 1,010.03 mi (1,625.48 km) |
| Helensburgh to Mogadouro | 1,018.44 mi (1,639.02 km) |
| Helensburgh to Moimenta da Beira | 1,047.05 mi (1,685.07 km) |
| Helensburgh to Moita | 1,215.74 mi (1,956.54 km) |
| Helensburgh to Moncao | 977.85 mi (1,573.70 km) |
