Mitten (Gloves)

Heat loss scales with surface area, and that is the main reason for a mitten. Four fingers sealed into a single compartment present much less outside surface than four fingers wrapped separately, and each one warms its neighbors instead of fighting the cold alone. Only the thumb gets its own housing, without which you could not hold anything at all.

The build is simpler than a glove and the simplicity helps. There are no fourchettes, the narrow strips that form the sides of each finger on a glove. A mitten has far fewer seams for cold to leak through and far more room inside for insulation. Loft, meaning the thickness of the trapped air layer, is what actually keeps you warm, and a mitten has the space to carry it. Serious cold-weather designs are mittens rather than gloves, usually a waterproof shell over a removable liner.

Ranked by warmth, a mitten beats a knit glove and a lined leather glove made of the same materials by a wide margin, and surrenders almost all fine control in exchange. Convertible mittens fold the top back to free your fingers, but the hinge and the extra seams cost some of that warmth advantage. Fingerless gloves sit at the far opposite end, all dexterity and almost no protection.

Deep cold, long exposure and children are the clear cases. A child cannot line up four fingers into separate stalls anyway, and small hands lose heat fastest. Avoid them if your day involves keys, card readers, buttons or a camera, because you will end up holding the mitten in your teeth.

Cuff length matters before anything else, since a gap at the wrist undoes the rest of the design. A cuff that overlaps your sleeve by two inches or more, with a drawcord or elastic, keeps the warm air in. Turn removable liners inside out to dry after a cold day, as sweat trapped in the liner is why a mitten feels clammy on day two.