| Merthyr Tudful to Jeffersonville (Indiana) | 3,903.72 mi (6,282.43 km) |
| Merthyr Tudful to Jenison (Michigan) | 3,699.59 mi (5,953.92 km) |
| Merthyr Tudful to Jenks (Oklahoma) | 4,419.88 mi (7,113.11 km) |
| Merthyr Tudful to Jennings (Missouri) | 4,065.35 mi (6,542.54 km) |
| Merthyr Tudful to Jensen Beach (Florida) | 4,215.77 mi (6,784.63 km) |
| Merthyr Tudful to Jericho (New York) | 3,300.91 mi (5,312.30 km) |
| Merthyr Tudful to Jerome (Idaho) | 4,723.75 mi (7,602.14 km) |
| Merthyr Tudful to Jersey City (New Jersey) | 3,325.54 mi (5,351.93 km) |
| Merthyr Tudful to Jessup (Maryland) | 3,505.28 mi (5,641.20 km) |
| Merthyr Tudful to Johns Creek (Georgia) | 4,047.52 mi (6,513.85 km) |
| Merthyr Tudful to Johnson City (New York) | 3,343.00 mi (5,380.04 km) |
| Merthyr Tudful to Johnson City (Tennessee) | 3,863.13 mi (6,217.11 km) |
| Merthyr Tudful to Johnston (Iowa) | 4,055.93 mi (6,527.38 km) |
| Merthyr Tudful to Johnstown (Colorado) | 4,529.66 mi (7,289.79 km) |
| Merthyr Tudful to Johnstown (Pennsylvania) | 3,540.54 mi (5,697.95 km) |
