Shoulder Strap

A shoulder strap carries 9 to 12 inches of drop, enough for the strap to sit on one shoulder while the bag rests under the arm. Nine inches is about the minimum that clears the shoulder of a coat, and it lands the bag at the waist. Twelve inches drops it to the hip, where it swings more but stops pressing on the ribs.

One shoulder takes the entire load, held in place by a small permanent shrug you stop noticing until evening. That asymmetry is the cost. Above roughly 3 kg the muscle across that side tires within the hour. Most people compensate by lifting the shoulder, which is exactly what causes the ache. Swapping sides every twenty minutes helps more than any amount of padding.

Strap width does the work padding gets credit for. A 1.5 inch strap spreads a load across three times the area of a half inch one. Meanwhile a chain concentrates the same weight into hard links that press through a thin coat and catch hair. Where the strap meets the bag matters just as much. It should anchor to a reinforced tab or the bag's own structure, never to a lining seam. That join carries everything. Check the underside of the strap too, because slick leather and smooth chain slide straight off a wool coat while suede or textured backing stays put.