CBM to Kg: How to Calculate Chargeable Weight for Sea Freight

In Air Freight, weight is everything. In Sea Freight, volume is king. However, there is a limit. If you ship something incredibly heavy (like iron dumbbells or granite slabs), the shipping line won’t charge you by size—they will charge you by weight.

This is determined by the CBM to KG conversion ratio. In this guide, we explain the “Chargeable Weight” rules for Sea Freight (LCL) so you don’t get hit with unexpected fees.

The Sea Freight Standard: 1 CBM = 1,000 KG

For ocean freight (LCL), the standard density ratio is 1:1000. This means shipping lines assume that 1 Cubic Meter of freight weighs 1,000 Kilograms (1 Ton).

How Billing Works (W/M)

Freight forwarders invoice based on W/M (Weight or Measure). They compare the volume (CBM) vs. the Weight (Tons) and charge whichever is higher.

Scenario A: Light Cargo (The Most Common)

You are shipping 5 CBM of cotton t-shirts. The total weight is 500kg.

• Volume: 5 CBM
• Weight: 0.5 Tons (500kg)

Comparison: 5 (Volume) is greater than 0.5 (Weight). Chargeable Volume: You pay for 5 CBM.

Scenario B: Heavy Cargo

You are shipping 2 CBM of steel bolts. The total weight is 3,500kg.

• Volume: 2 CBM
• Weight: 3.5 Tons (3,500kg)

Comparison: 3.5 (Weight) is greater than 2 (Volume). Chargeable Volume: You pay for 3.5 CBM (even though it physically only takes up 2 CBM).

Why This Matters for Pricing

If your cargo is dense (heavy), quoting based on dimensions alone will give you the wrong price. You must know the weight.

The formula to check your Chargeable Weight:

Chargeable Weight (Tons) = Actual Weight (kg) / 1000

Compare this number to your CBM. The higher number is what appears on your invoice.

Differences in LCL vs. Express Courier

It is important not to confuse Sea Freight rules with Courier rules (DHL/FedEx).

• Sea Freight: 1 CBM = 1000 KG
• Air Freight/Express: 1 CBM = 167 KG (approx)

This is why sea freight is so much cheaper for heavy items. It tolerates much higher density before the price increases.

Key Takeaway

For 90% of Amazon FBA sellers shipping standard products (electronics, home goods, toys), your CBM will almost always be higher than your weight in tons. You will pay by CBM. However, if you are sourcing metals, liquids, or ceramics, always check the weight.