Most landed cost spreadsheets fail in the same place: they total the shipment and divide by units. That works only if you imported one product. The moment a container holds several SKUs, the shared costs have to be allocated — and the basis you choose changes per-unit cost dramatically. Allocate freight by value and your expensive items absorb it. Allocate by volume and your bulky items do. Same shipment, same invoice total, very different answers about which product actually makes money.
Landed Cost Calculator handles the multi-SKU case properly. Enter each product with its price, quantity, weight, volume and its own duty rate, then set the allocation basis independently for each cost category — freight by weight because that is what carriers bill, insurance by value because that is what underwriters charge, brokerage per line because that is how it is invoiced. Duty is never allocated; each SKU pays its own rate on its own value.
It then adds the costs that most models omit entirely. The financing cost of money tied up between paying your supplier and selling the goods, which on long transits routinely exceeds the freight difference between carriers. The currency spread you actually transact at rather than the mid-market rate. And a damage allowance, so that the saleable units carry the cost of the ones that arrived broken. The output is true landed cost per unit, the selling price required for your target margin, and sensitivity tables showing how much of that margin belongs to the exchange rate rather than to your buying.