THE chief engineer included in the design criteria that the vehicle could carry four 190cm-tall adults. The vehicle was designed to maximise interior space within a short overall length. Echo has an overall length of 3615mm, a height of 1510mm and a wheelbase of 2370mm. Echo hatch has 1317mm of front shoulder room and 1288mm of rear shoulder room. Headroom dimensions are 1013mm front and 955mm rear. The hatch's legroom dimensions are 1044mm front and 885mm rear.

Vehicle entry and exit has been optimised by the 1510mm roof height, which allows for higher door openings.