The Fit uses Honda's Global Small Car platform, which is also used by the Fit Aria/City (a sedan version of the Fit), the Airwave (a wagon version of the Fit Aria/City), the Mobilio, and the Mobilio Spike. One of the characteristics of the Fit, which is also present in the Fit Aria and Airwave, is the location of the fuel tank. Rather than placing it under the rear seats, it is located under the front seats, thereby freeing up valuable room in the back. It also allows for Honda’s "Magic Seat" system, called ULTR seat in Japan, which has five distinct seating modes:

• Normal: seats are in their normal position with seating for five.
• Utility: Either section (or both) of the 60:40 split rear seat sink down into the rear foot well as the rear seat back is lowered forward. This offers a low, perfectly flat surface that increases the cargo area substantially.
• Long: The rear seat behind the passenger folds down similar to utility mode, but the front passenger seat folds backward, leaving an area that can hold items as long as 2.4 meters (7.9 ft).
• Tall: Either section (or both) of the rear seat cushion fold up against the rear seat back, allowing for an area of 1.28 meters (4.2 ft) in height.
• Refresh: With the headrest of the front seat removed, the front seat back can be folded down to form a lounge-style sitting area.