A chunky jumper suits anyone who runs cold, anyone who likes a bit of structure to hide behind on a day when nothing else feels right, and anyone who wants one item to do the job of a coat and a cardigan at once. It's less kind to anyone working somewhere warm all day, under lights or near ovens, because the whole point of the thing is insulation, and insulation doesn't switch off just because you've gone pink in the face. If you're petite and already feel swamped by layers, go carefully too, since a proper chunky knit adds bulk in every direction, not just width.
If you own none, start with one in a mid grey or oatmeal, in a wool and acrylic blend rather than pure wool or pure cotton. Pure wool chunky knits look glorious on the hanger and then itch at the neck by eleven in the morning, and pure cotton ones, however soft, sag at the elbows within a fortnight and never spring back. A blend with a bit of acrylic or nylon in it holds its shape through a full day of sleeves pushed up and down, and survives a cool machine wash without turning into something you'd put on a smaller woman entirely.
Once you've got the plain one, it pairs with almost everything you already own on the bottom half, which is the real value of it. Straight leg jeans, a longer denim skirt, wide trousers, even a slip skirt on a warmer day with the jumper doing the work a coat usually does. Tucking the front in, just the front, is the trick that stops you looking like you're wearing a tent, and it takes about two seconds once you know to do it. Boots ground the whole look, trainers make it look like you've just finished a long walk, both are correct depending on the day.
This is an autumn and winter piece through and through, not something you're fighting into in June. It earns its keep on the days that are cold but not coat weather, on train platforms, on school runs, on any day where you're in and out of heated buildings and need something you can shove the sleeves up on rather than peel off entirely.
Over time, a good one softens rather than wears out, the wool relaxing into the shape of your arms and shoulders, the collar loosening just enough to stop being fussy at the neck. The bad ones bobble within a month and never recover. The good ones get better looking the longer you leave them folded on the chair instead of the hanger.