The Audi A1 Sportback has grown significantly in length - with an additional 56 millimeters (2.2 in), it now measures 4.03 meters (13.2 ft). At the same time, the width has remained almost the same at 1.74 (5.7 ft) meters. The new-generation model is only 1.41 meters (4.6 ft) in height - including aerial, the car is 1.43 meters (4.7 ft) tall. The wide track and short overhangs provide for a taut, sporty look. The wide, low-placed Singleframe grille and the implied side air inlets dominate the distinctive front. Below the edge of the hood are three flat slits - an homage to the Sport quattro, the brand's rally icon from 1984.

The new Audi A1 Sportback also emphasizes a resemblance to the Audi Ur-quattro and Sport quattro when viewed from the side: The wide, flat sloping C-pillar seems to push the car forward even while standing still. The roof contrast line, which is available in two dark colors, ends above the C-pillar. This gives the impression that the roof is flatter and the complete car is even lower-slung. All lines on the flanks, from the window edge to the sill, slope upward toward the rear in a wedge shape. The distinctively highlighted wheels and the low shoulder line in between give the A1 Sportback a solid stance on the road. The low line between the fender edges draws the visual focal point downward even further.