| Merthyr Tudful to McKeesport (Pennsylvania) | 3,577.22 mi (5,756.98 km) |
| Merthyr Tudful to McKinleyville (California) | 5,112.17 mi (8,227.25 km) |
| Merthyr Tudful to McKinney (Texas) | 4,588.17 mi (7,383.94 km) |
| Merthyr Tudful to McLean (Virginia) | 3,531.53 mi (5,683.45 km) |
| Merthyr Tudful to McMinnville (Oregon) | 4,843.31 mi (7,794.56 km) |
| Merthyr Tudful to McMinnville (Tennessee) | 4,032.40 mi (6,489.52 km) |
| Merthyr Tudful to McNair (Virginia) | 3,540.10 mi (5,697.24 km) |
| Merthyr Tudful to McPherson (Kansas) | 4,365.30 mi (7,025.27 km) |
| Merthyr Tudful to Mead Valley (California) | 5,304.67 mi (8,537.05 km) |
| Merthyr Tudful to Meadow Woods (Florida) | 4,206.21 mi (6,769.24 km) |
| Merthyr Tudful to Meadowbrook (Virginia) | 3,611.20 mi (5,811.67 km) |
| Merthyr Tudful to Meadville (Pennsylvania) | 3,531.85 mi (5,683.97 km) |
| Merthyr Tudful to Mebane (North Carolina) | 3,747.39 mi (6,030.85 km) |
| Merthyr Tudful to Mechanicsville (Virginia) | 3,597.43 mi (5,789.50 km) |
| Merthyr Tudful to Medford (Massachusetts) | 3,132.46 mi (5,041.21 km) |
