The 3 hatchback's boot is slightly smaller than a VW Golf's, at 364 litres with the rear seats in place and 1263 litres with them folded. In practical terms that's more than enough for a large weekly shop to sit behind the seats, and you shouldn't have too much trouble squeezing in a set of golf clubs or the chassis and seat of a buggy.
The space is reasonably square, although the rear wheel arches do intrude at the side and Mazda doesn't supply any baggage hooks to keep your shopping from rolling around. There's a high lip to lift loads over, too, which won't be helpful if you're dealing with heavy items.
The 3 Fastback version (in effect a small saloon) has a slightly larger overall capacity (419 litres) but while the bootlid does move right up out of the way when you open it, the aperture that it leaves still isn't anywhere near as convenient as the hatchback's.
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