How wide is the river Thames?

The width of the River Thames varies along its course. At its widest point, near the Isle of Grain in Essex, the river is approximately 1 mile (1.6 kilometers) wide. However, at its narrowest point, near Mapledurham Lock in Oxfordshire, the river is only about 200 feet (61 meters) wide. On average, the River Thames is about half a mile (0.8 kilometers) wide.