The Mazda3 sedan measures out to 94.3 cubic feet of passenger space, which compares with the Honda Civic sedan's 90.9 cubic feet. Both the Mazda and the Honda are within fractions in front-seat room, but the Mazda is slightly larger in rear-seat room, notably leg room and shoulder room. The Civic and Mazda3 are virtually identical in trunk volume, with the Mazda rated at 11.4 cubic feet.

The Mazda3 five-door might be compared to a Subaru Impreza Sport Wagon, especially since each is the basis of a high-performance car, the Mazdaspeed3 and Subaru Impreza Wagon WRX respectively. The Mazda3 five-door has 95.3 cubic feet of interior volume, while the Subaru is rated at 90.4 cubic feet. Just as with the sedan, the Mazda's advantage lies in rear seat room, notably leg room and shoulder room. Meanwhile the Subaru's cargo volume behind the second seat is about a cubic-foot larger than the Mazda's 17.1 cubic feet.

The utility of the Mazda3's interior is enhanced by a standard folding 60/40 split back seat, which enables you to increase trunk room for large loads. The back of the rear seat doesn't quite fold flat, but it's close. Thanks to this design, the Mazda3 five-door will accommodate 31.2 cubic feet of cargo behind the front seats when the second seat is folded down.

The Mazda3 seats themselves are supportive without being confining, and the use of high-quality foam in the bolsters makes them very comfortable during long drives. Every version of the Mazda3 except for the entry-level sedan features a height adjuster for the driver's seat, and this works with the standard tilt/telescoping steering wheel to enable a wide range of drivers to get a good fit with the controls. Grand Touring editions feature seat warmers. Leather seat upholstery comes standard on Grand Touring models and optional on Touring and Sport editions.

When it's well-equipped with trim and features, the interior of the Mazda3 looks good, although black interiors seem very dark. For s-models, a brushed aluminum surface lends some drama to the dashboard, as does the use of using red-orange electro-luminescent numerals with blue-tinted dials for the instruments. For 2007, Mazda has upgraded the appearance of the i-model sedans with wood trim for the dash and new white-face instrument gauges, and they look very good in light colors.

The Mazda3 affords plenty of practical space, notably a cavernous glovebox. Two built-in cupholders are integrated into the center console, while a small but deep box separates the seats. For 2007, rear-seat armrests with integrated cupholders have been added for both the sedan and five door. Also new for 2007 is an iPod-friendly auxiliary input jack for the audio system including a 12-volt power outlet.

The navigation display screen flips up from the top of the dash, and it offers a bright view, while the software logic for entering destinations and the like is straightforward. The navigation system's controls are located in the center console, however, and they're small and fussy enough (especially the joystick control) to be a chore to operate. The Mazda3 is one of the very few cars in this price class to offer a navigation system.

The Mazdaspeed3's black, leather-trimmed interior has the same overall look as its siblings, but red stitching in the steering wheel, shift knob and seats adds some motorsports style. The thick rim, leather-wrapped rim of the steering wheel feels substantial, while aluminum covers for the control pedals enhance the presentation. The best thing about the Mazdaspeed3's interior is the high-bolstered sports seats, which cradle and support rather than confine. The strategic use of leather and cloth inserts keeps you from inadvertently sliding around when you're driving at a quick pace. These are the kind of seats that will help you rack up a thousand miles of driving in a day.