| Watford to Ickenham | 7.07 mi (11.38 km) |
| Watford to Ifield | 37.62 mi (60.54 km) |
| Watford to Ilford | 21.73 mi (34.97 km) |
| Watford to Ilfracombe | 163.36 mi (262.89 km) |
| Watford to Ilkeston | 98.77 mi (158.95 km) |
| Watford to Ilkley | 167.77 mi (270.01 km) |
| Watford to Immingham | 135.55 mi (218.15 km) |
| Watford to Ince-in-Makerfield | 159.72 mi (257.05 km) |
| Watford to Inverness | 430.39 mi (692.65 km) |
| Watford to Inverurie | 396.69 mi (638.41 km) |
| Watford to Ipswich | 71.85 mi (115.64 km) |
| Watford to Irlam | 150.13 mi (241.61 km) |
| Watford to Irthlingborough | 47.15 mi (75.88 km) |
| Watford to Irvine | 324.81 mi (522.73 km) |
| Watford to Islington | 14.73 mi (23.70 km) |
