What Is Tare Weight? A Guide to Shipping Weights

Whether it’s tare weight, gross weight or volumetric weight, accurate weight calculations are one of the foundations of successful international trade.

Understanding the differences between them and how they’re calculated can mean the difference between profitable operations and costly delays.

In this guide, you’ll learn everything you need to know about shipping weights, including how to calculate them and why they matter. Let’s dive in.

What is tare weight?

Tare weight, also called unladen weight, is the weight of an empty container or pallet prior to shipping. In bulk transport, it can also mean the weight of an empty transport vehicle, measured using a weighbridge.

For example, a standard 20-foot shipping container has a tare weight of around 2,280 kg. A 40-foot container weighs around 3,700 kg.

Knowing the tare weight helps us calculate the actual weight of the cargo, which impacts freight quotes and shipping costs. It’s also used in customs clearance processes and health and safety policies.

What is net weight?

Net weight in shipping is the actual weight of cargo or products, excluding packaging materials, containers and any shipping accessories. It’s also called net mass or payload.

Net weight is the most important number for customs clearance. It’s what officials use to calculate import duties and taxes. Accurate calculations avoid custom delays and penalties.

What is gross weight?

Gross weight is the total weight of a shipment, including the cargo, packaging materials, pallets and containers. It’s the sum of the net weight and tare weight.

The only thing gross weight doesn’t include is the transport vehicle itself.

Many ocean freight and air freight shippers base their charges on gross weight. The weight limits on lorries are also usually based on gross weight. Warehouses use gross weight to load containers safely and prevent damage during transport.

What is volumetric weight?

Whilst tare, net and gross weight represent actual physical measurements, volumetric weight is based on the space a package occupies rather than what it weighs on a scale.

It’s a pricing technique that prevents large, lightweight parcels from consuming valuable cargo space without covering their fair share of transport costs.

Carriers use the following formula to calculate volumetric weight:

Volumetric weight = (length × width × height) ÷ dimensional factor

The dimensional factor (also called the 'dim factor' or 'volumetric constant') varies between carriers and transport methods. For example, in sea freight, it’s often 1,000 cm³/kg, and in air freight, it’s 6,000 cm³/kg.

Carriers compare both net and volumetric weight and use whichever is greater when calculating shipping fees. This system ensures fair pricing, whether you're shipping a box of feather pillows or a crate of heavy metal components.

How to calculate shipping weights

If a carrier knows the weight of the container and the weight of the cargo, it’s easy to calculate gross weight using the following formula:

Gross weight = net weight + tare weight

For example, if you’re shipping 20,000 kg of cargo in a standard 20-foot container weighing 2,300 kg, the gross weight will be 22,300 kg.

The calculation works multiple ways:

• Tare weight = gross weight - net weight

• Net weight = gross weight - tare weight

If you know two of the figures, you can easily calculate the third.

Why knowing your shipping weight matters

The successful movement of your goods depends on these measurements. Accurate calculations impact costs, profitability, penalties and safety:

• Accurate cost calculations. Shipping costs and import duties are based on the net and gross weight of your goods. Knowing both is vital for accurate shipping costs and speedy customs clearance.

• Avoiding penalties. Incorrect weight declarations can lead to unexpected surcharges, penalties and delays. In some cases, containers may be rejected at ports.

• Regulatory compliance. The International Maritime Organisation's SOLAS regulations require Verified Gross Mass declarations for all packed containers before loading onto vessels.

• Safety concerns. Incorrect weight distributions can cause container securing equipment failure, leading to cargo loss during transport. UK road regulations impose strict axle weight limits, with legal maximums of 11.5 tonnes for single drive axles. Overloaded vehicles face penalties and pose safety risks to infrastructure and other road users.

How do carriers use shipping weights to calculate costs?

Modern shipping carriers use different calculation methods to determine chargeable weights across each transport mode:

Ocean freight

In ocean freight, carriers use tare weight to ensure compliance with weight restrictions, determine accurate shipping costs and calculate maximum payload capacity.

Air freight

Tare weight is vital in air freight due to strict weight limits. Carriers use tare weight to maximise payload, ensure accurate fuel calculations and calculate shipping fees.

Road freight

In road transport, shippers use tare weight and gross weight to ensure compliance with road weight restrictions and to calculate fuel costs and shipping fees.

What are some common shipping weight challenges and misconceptions

Shipping weight misconceptions can lead to miscalculations and costly errors.

Approximate weight calculations

One of the most significant issues is approximate weight declarations. Many businesses falsely assume that rough estimates will suffice when completing shipping documentation. But this almost always results in delays, fines and safety issues.

Incorrect packaging weight

Packaging weight assumptions are another issue. Businesses often underestimate the weight of protective packaging material and pallets when sending goods. Where goods require extensive protection, packaging can constitute a substantial portion of the total gross weight.

Volumetric weight

Volumetric weight also causes confusion among importers and exporters. Many focus solely on the weight of their goods, rather than taking dimensional considerations into account.

Large, lightweight goods often incur charges based on the space they consume rather than their weight. This creates a gulf between expected and actual shipping costs, with some importers struggling to make up the difference. As a result, it’s vital to understand when volumetric weight applies.

Ship seamlessly with Pro Carrier

Calculating shipping weights is a complicated affair for most importers and exporters. That’s why so many work with third-party logistics providers like Pro Carrier.

Our expertise in navigating the complexities of international trade means you never have to worry about weight calculations, limits or paperwork ever again.

We manage all shipping and customs documentation on your behalf, ensuring accurate calculations, compliance and expedited customs clearance. We even work two weeks ahead of sailing schedules, where possible, to prevent delays.

Cutting-edge technology, like our Horizon tracking platform, means you’re always in control and can manage everything from a single dashboard. So whether you’re shipping FCL, LCL or in bulk, you can trust us to deliver your goods using the most optimal approach.

For more information on how we can help, read our case studies or contact one of our experts today.