Ocean freight sounds dramatically cheaper and is, per kilogram, but the fixed costs at both ends mean it only becomes worthwhile well above the weight most people are shipping. Knowing the crossover point stops you from either overpaying for air or waiting ten weeks unnecessarily.
The cost structures are not comparable per kilogram
Air freight from Korea to the US is priced roughly 7 to 13 USD per kilogram depending on weight band, with modest fixed costs. Sea freight for a small consignment might be 2 to 4 USD per kilogram, but adds port handling, documentation, destination terminal charges and inland delivery that together commonly run 300 to 600 USD regardless of volume. Those fixed charges are what determine the break-even.
Where the break-even actually falls
For most personal shipments the crossover sits somewhere around 100 to 150 kg. Below that, air is usually cheaper once the sea-side fixed costs are counted. Above roughly 200 kg, sea shipping wins decisively and the gap widens quickly. A shared container arrangement lowers the fixed costs and moves the break-even down somewhat.
Time and what it costs you
Ocean transit from Korea to the US west coast is typically 14 to 21 days at sea, plus one to two weeks of consolidation before departure and one to two weeks of clearance and inland delivery afterward. Realistic door to door is six to ten weeks against five to ten days for air. For a household move that is fine; for inventory it is a working capital problem.
What should never go by sea
Anything time-sensitive, anything you might need before the box lands, and anything vulnerable to humidity. Containers experience significant temperature and moisture swings, and paper goods, photographs and some cosmetics do not enjoy six weeks of it. Pack anything paper-based with desiccant and sealed bags if it must go by sea. Musical instruments, wooden furniture and leather goods are also poor candidates, since humidity swings warp and mildew them over a six week crossing.
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Start a buy-for-me order →Frequently asked
Can I ship a few boxes by sea?
Technically yes as part of a consolidated container, but the fixed charges make small ocean shipments poor value. Under about 100 kg, air is nearly always the better answer.
Is sea freight safer or riskier?
Handling damage risk is comparable; moisture and long-duration risks are higher. Insurance is priced accordingly and is worth carrying on any large ocean shipment.
How far ahead do I need to book?
Consolidation schedules mean a departure window rather than a departure date, so allow two to three weeks between deciding and sailing.