| Harpenden to Mickleover | 90.37 mi (145.43 km) |
| Harpenden to Middlesbrough | 194.11 mi (312.39 km) |
| Harpenden to Middleton | 142.52 mi (229.37 km) |
| Harpenden to Middlewich | 129.41 mi (208.26 km) |
| Harpenden to Midsomer Norton | 98.62 mi (158.71 km) |
| Harpenden to Mildenhall | 51.61 mi (83.06 km) |
| Harpenden to Milford Haven | 200.65 mi (322.92 km) |
| Harpenden to Mill Hill | 14.62 mi (23.52 km) |
| Harpenden to Milngavie | 327.36 mi (526.83 km) |
| Harpenden to Milnrow | 144.07 mi (231.86 km) |
| Harpenden to Milton | 113.72 mi (183.02 km) |
| Harpenden to Milton Keynes | 23.19 mi (37.33 km) |
| Harpenden to Minehead | 140.75 mi (226.52 km) |
| Harpenden to Minster | 56.86 mi (91.50 km) |
| Harpenden to Mirfield | 140.34 mi (225.85 km) |
