How to Calculate Volume & Weight for Ocean Freight

A Practical Chargeable Weight Guide (CBM, Tons, W/M Explained)

If you ship ocean freight often—especially LCL (Less than Container Load)-knowing how to calculate volume (CBM) and weight (kg/tons) is essential. It helps you:

• estimate freight cost accurately,

• choose the right shipping method (LCL vs FCL),

• avoid surprises from re-measurement or re-weighing,

• plan packing to reduce chargeable units.

This guide walks you through the calculations step by step with real examples and conversion shortcuts.

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Key Terms You’ll See in Ocean Freight Quotes

CBM (Cubic Meter)

A unit of volume. Most ocean LCL pricing uses CBM as the “measure” component.

Gross Weight

The total weight, including product + inner packaging + outer cartons/crates/pallets.

Metric Ton (MT)

1 MT = 1,000 kg.

W/M (Weight or Measure)

The most common LCL rating rule:

• You are charged on whichever is greater:
  (Volume in CBM) or (Weight in metric tons)

RT (Revenue Ton) / Freight Ton

Many forwarders express LCL chargeable units as RT, where:

• 1 RT = 1 CBM or 1,000 kg (1 MT), whichever is higher.

In plain terms:
Chargeable units = max(CBM, Weight in MT)

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Ocean Freight: LCL vs FCL Charging Basics

LCL (Less than Container Load)

You share container space with other shippers. Costs are typically based on:

• chargeable units (W/M) +

• origin charges + destination charges + documentation, etc.

Your job: calculate CBM and weight correctly, then compare.

FCL (Full Container Load)

You usually pay per container (20’, 40’, 40’HC), not per CBM.
But volume and weight still matter for:

• choosing container size,

• staying within max payload limits,

• complying with VGM (Verified Gross Mass) rules,

• avoiding overweight surcharges (road/port/carrier).

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Step-by-Step: How to Calculate CBM (Volume)

Step 1: Measure the outer dimensions

Use the packed dimensions (carton/crate/pallet), not product-only.

You need:

• Length (L)

• Width (W)

• Height (H)

Step 2: Convert to meters

CBM is in meters, so convert if needed.

Step 3: Apply the CBM formula

CBM per piece = L × W × H (in meters)

Step 4: Multiply by quantity

Total CBM = CBM per piece × number of pieces

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Quick Conversion Cheat Sheet

Helpful volume conversions

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Step-by-Step: How to Calculate Weight (for Ocean Freight)

Step 1: Get gross weight per piece

Use a scale if possible. If the factory provides weight, ensure it’s gross, not net.

Step 2: Multiply by quantity

Total gross weight (kg) = weight per piece × number of pieces

Step 3: Convert kg to metric tons (MT)

Weight in MT = total kg ÷ 1,000

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The Core Rule: How to Calculate Chargeable Weight for LCL (W/M)

Once you have both totals:

• Total CBM

• Total Weight in MT

Chargeable units = max(Total CBM, Total MT)

That number becomes the basis for the ocean freight line-haul (and sometimes other charges).

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Special Shapes: How to Calculate Volume for Cylinders (Drums/Rolls)

If you ship drums or rolls, use:

CBM = π × r² × h

Where:

• r = radius (meters)

• h = height/length (meters)

• π ≈ 3.1416

If you’re palletizing drums, most forwarders will rate on the outer pallet dimensions anyway-so measure the fully wrapped pallet.

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Rounding Rules: Why Your Quote May Not Match Your Calculator

Freight forwarders and co-loaders may apply rounding such as:

• rounding CBM up to the nearest 0.01 or 0.1

• rounding chargeable units up to a minimum (e.g., 1.0 RT minimum)

• applying minimum ocean freight charges even for very small shipments

Best practice: assume slight rounding upward and keep a buffer when budgeting.

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FCL Note: Volume & Weight Still Matter (Even If You Pay Per Container)

Even though FCL is “per container,” you still must stay within:

• container payload limits (varies by container and line),

• road weight limits (varies by country/port),

• port terminal restrictions,

• VGM requirements.

A common mistake is thinking: “If it fits, it ships.”
In reality: you can cube out (run out of space) or weigh out (hit max payload) first.

Practical tip: check the container’s CSC plate and the carrier/terminal rules for your specific route.

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Common Mistakes That Increase Chargeable Weight

1. Using product dimensions instead of packed dimensions
   Always measure cartons/crates/pallets as shipped.

2. Forgetting pallet overhang / stretch wrap
   The measured dimensions include the wrap and any bulges.

3. Mixing units (cm with m, inches with ft)
   Convert everything before calculating.

4. Not summing mixed package sizes correctly
   If you have different cartons, calculate CBM per type and add totals.

5. Assuming LCL is “priced by kg”
   It’s W/M, so bulky goods can cost more even if light.

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A Simple Checklist Before You Request a Quote

Send your forwarder:

• Number of pieces

• Package type (carton, crate, pallet, drum)

• Dimensions per piece (L×W×H)

• Gross weight per piece

• Total gross weight

• Cargo description (general goods / DG / battery, etc.)

• Pickup and delivery locations + Incoterms

The more precise your measurements, the fewer surprises you’ll get later.

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FAQ

Is “chargeable weight” the same for ocean and air freight?

The idea is similar (you pay on the higher of weight vs volume), but the formula and factors differ. Ocean LCL typically uses W/M: 1 CBM vs 1,000 kg.

What is 1 CBM in kg for ocean freight?

For LCL rating, 1 CBM is treated as equivalent to 1,000 kg (1 MT) for comparison purposes under W/M.

If my cargo is 0.6 CBM and 900 kg, what do I pay?

Compare:

• CBM = 0.6

• Weight in MT = 900/1000 = 0.9
  Chargeable = 0.9 RT (weight wins)

(Then apply any minimum charges/rounding rules.)

Do pallets reduce chargeable volume?

Sometimes pallets increase chargeable volume because they add height/footprint. If your cartons can be floor-loaded safely, it might reduce CBM-but pallets can reduce damage and speed handling.

For FCL, do I need CBM at all?

Yes-for load planning, container selection, and to avoid overweight issues.