The bridge is 800 feet (240 metres) in length with two towers each 213 feet (65 metres) high, built on piers. The central span of 200 feet (61 metres) between the towers is split into two equal bascules or leaves, which can be raised to an angle of 86 degrees to allow river traffic to pass. The bascules, weighing over 1,000 tons each, are counterbalanced to minimise the force required and allow raising in five minutes.
The two side-spans are suspension bridges, each 270 feet (82 m) long, with the suspension rods anchored both at the abutments and through rods contained within the bridge's upper walkways. The pedestrian walkways are 143 feet (44 m) above the river at high tide.
The main bridge deck carries two lanes of road traffic between two low-level pedestrian walkways across both suspension spans and the opening bascule section of the bridge, with the walkways separated from the roadway by fences. The roadway passes through each of the two towers, whereas the low-level walkways pass around the outside of the towers.
One of the 'chimneys' on the bridge, which are often confused as lamposts, connects up to an old fireplace in a guardroom of the Tower of London. It is long-disused.