shipping_length

Dimensional weight pricing — where carriers charge based on whichever is greater (actual weight or dimensional weight) — depends on accurate length, width, and height. Without all three populated, channels and carriers default to assumed dimensions, often inflating shipping cost calculations.

The carrier billing reality: dim weight = (L × W × H) / divisor, where divisor varies by carrier (usually around 139 for inches or 5000 for cm). For lightweight but voluminous items (pillows, foam mattresses, packaging-heavy products), dim weight typically dominates actual weight, and getting it right matters more than the actual weight does.

The packaging-vs-product distinction: feed dimensions should reflect packaging dimensions, not product dimensions. Carriers ship in rectangular boxes; the bounding box determines shipping cost. A small product in oversized packaging gets shipped at the packaging's dim weight, not the product's.