A structured evening clutch holds a phone, a card holder, one lipstick and a key. That is the honest capacity of most of them, and the rigid ones hold less than they look like they will, because the shape does not give.

The measurement that decides it is depth, not width. A clutch can be 25cm across and still refuse a modern phone, because the internal depth is under 2cm once the frame and lining are accounted for. Large phones are the usual failure: a 16cm phone needs a clutch whose longest internal dimension is genuinely longer than that, and the case adds a few more millimetres. If you carry a big phone, measure it and then look at the listed dimensions rather than the photograph.

What does not fit, in almost any of them: a full-size wallet, sunglasses in a case, a hairbrush, a paperback, a water bottle, keys on a large ring. Soft pouch styles are more forgiving than hard frames, because they flex around what you put in.

So the real question is not how much a clutch holds. It is whether you are willing to carry only that.

If you need your hands, buy a shoulder bag. This sounds obvious, but the specific moments matter: holding a drink and greeting people, managing a coat, standing through a ceremony, getting a phone out repeatedly for photographs. A clutch occupies one hand permanently, or it goes under an arm and slides.

A convertible style solves most of this. A clutch with a removable chain gives you the evening silhouette when you are seated and a shoulder bag when you are not, and the chain hides inside afterwards. If you buy one bag for occasions, buy that one.

The other case for sizing up is a long day rather than an evening. Weddings run twelve hours, and by hour eight you want a lipstick, a plaster, a phone at 4% and a charger. Nothing rigid takes a charger.

Small shoulder and crossbody bags now cover the same formality as a clutch, which was not true a decade ago. A sculptural shoulder bag in the same finish reads just as dressed.

Work backwards from the outfit and the length of the event. A hard frame in a strong shape is the right buy for a two-hour dinner or a party where you will not be carrying anything else. It photographs better than anything soft, and it holds its line for years because there is nothing to slouch.

A soft pouch or wristlet is the more practical evening buy. It takes a slightly bigger phone, packs flat in luggage, and a wrist strap means you can eat without putting it on the floor.

For anything all-day, choose a small crossbody and accept the strap in your photographs. The comfort difference over eight hours is enormous.

One practical note on materials. Woven, bamboo and open-frame styles look wonderful and hold almost nothing securely, so a small internal pouch is worth adding for cards and cash. Anything with a rhinestone or a lacquered finish should travel in the dust bag, because the whole appeal is a surface that has not been scratched.

Most people own one clutch too many and one small shoulder bag too few. The clutch gets bought for a specific event, comes out twice, and then sits there because it cannot carry a day.

If you are buying one bag for occasions, buy the convertible: chain on for the day, chain off for the dinner. If you are buying for a specific evening and you already own something practical, buy the rigid sculptural one and enjoy it, knowing it holds a phone, a card and a lipstick.

If you take one thing away: measure your phone against the listed internal dimensions before you buy, because that single number decides whether the bag works at all.