Dimensional Weight: Why Your Light Parcel Costs So Much to Ship

What Is Dimensional Weight?

Dimensional weight (DIM weight, also called volumetric weight) is a pricing technique used by all major couriers. It reflects the amount of space a package occupies relative to its actual weight.

The logic is simple: a large, lightweight box takes up just as much space on an aircraft as a small, heavy one. Couriers charge based on whichever is greater — actual weight or dimensional weight.

The Formula

Dimensional Weight (kg) = Length x Width x Height (cm) / 5000

FedEx uses a divisor of 5000 for international shipments. Some carriers use different divisors.

Example

A box measuring 50cm x 40cm x 30cm containing a 2kg item:

• Actual weight: 2kg
• DIM weight: (50 x 40 x 30) / 5000 = 12kg
• Billable weight: 12kg (DIM weight is higher)

You'd be charged for 12kg even though the package only weighs 2kg. That's a 6x price multiplier.

How to Reduce Dimensional Weight

• Use the smallest box possible. Don't use a shoe box for a phone case. Match the box size to the contents.
• Reduce void fill. Less empty space means a smaller box. Use cushioning materials that compress well.
• Use poly mailers for soft goods. Clothing, fabric items, and non-fragile soft goods can ship in poly bags instead of boxes — no dimensional weight applies to mailers.
• Flatten where possible. If your product can ship flat rather than in a 3D box, the savings are significant.
• Consolidate items. Two items in one compact box costs less than two separate shipments.

Quick Reference: DIM Weight by Box Size

• 30x20x15cm = 1.8kg DIM
• 40x30x20cm = 4.8kg DIM
• 50x40x30cm = 12.0kg DIM
• 60x40x40cm = 19.2kg DIM
• 80x60x40cm = 38.4kg DIM

Pro Tip: Measure Before You Quote

Always enter accurate dimensions when getting a shipping quote. If your dimensions are wrong, the carrier will re-measure at the sorting facility and charge you the difference — plus a correction fee.

ShipAnywhere calculates DIM weight automatically when you enter your package dimensions, so you always know the billable weight before you pay.