Volumetric weight: why a half-empty box still costs you money
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by Verpakkingdeals.nl
6 min reading time
Many carriers don't just charge based on what the scale shows, but also on the space your box takes up. Here's how to calculate your volumetric weight and how to reduce it.
You weigh a package at 900 grams, choose a rate up to a kilo, and suddenly the bill says three kilos. That's not a carrier error. With many shipping services, not only does the scale matter, but also how much space your box occupies in the delivery van. This second number is called volumetric weight, and it is one of the quietest cost items in a webshop. You don't see it on your box or on your scale, but you do see it on your invoice.
What volumetric weight actually is
A delivery van gets full faster than it gets heavy. A pallet of feathers takes up as much space as a pallet of stones, while the former weighs almost nothing. Carriers solve this by giving your package two weights: the actual weight and a weight derived from the dimensions. The highest of these two is the weight you will be charged for.
FedEx describes the calculation method for the Netherlands as length multiplied by width multiplied by height, divided by a divisor, with 5000 being the most commonly used divisor for centimeters. If the actual weight is higher than the volumetric weight, the actual weight is used. Other carriers use the same system, but not always the same divisor. So check your own contract or price list to see which factor applies to you, because that one number determines how much an empty centimeter costs you.
The calculation, with real box dimensions
The formula is simple: multiply the three external dimensions in centimeters, divide by 5000, and you have the volumetric weight in kilograms. Below are a few sizes from our own assortment, calculated.
Packaging
Outer dimensions
Volume
Volumetric weight
Mailbox box A6
18 x 11.5 x 2.8 cm
580 cm³
0.12 kg
Flat shipping box
15 x 10 x 4 cm
600 cm³
0.12 kg
Mailbox box A5+
25.5 x 16 x 2.8 cm
1,142 cm³
0.23 kg
Cube box
15 x 15 x 15 cm
3,375 cm³
0.68 kg
Moving box 50 liters
48 x 43 x 33 cm
68,112 cm³
13.62 kg
Look at the last two lines. The Cardboard Shipping Box 15x15x15 cm (€1.99) has almost six times the volume of a flat box measuring 15 x 10 x 4 cm, while the cardboard itself weighs barely more. And an Action Moving Box 480x430x330 mm (€3.50) already comes in at over thirteen kilos of volumetric weight when empty. If you send a few sweaters in it, you pay for thirteen kilos of air.
When it affects you and when it doesn't
For regular Dutch parcel post, you often don't notice it much, because fixed formats are used. PostNL, for example, uses a letterbox parcel up to 2 kg with a maximum of 38 x 26.5 x 3.2 cm for domestic shipments, a small parcel up to 3 kg (38 x 28 x 15 cm) and an average parcel up to 10 kg (100 x 50 x 50 cm). You fall into a class, and that class determines the price.
Volumetric weight becomes important as soon as you step outside this fixed framework. Think of business rates with tiered pricing per kilo, couriers and express services, and international shipments. Also, for pallets and larger shipments to a store or wholesaler, volume is almost always the determining factor. The further your package travels and the more links it passes through, the greater the chance that space will be charged for instead of kilos.
Four interventions that really reduce your volumetric weight
1. Go from high to flat
Height is the dimension you usually lose most easily. A cube box fills with air above the product; a flat box does not. For clothing, books, jewelry, and accessories, a Red Shipping Box 13.5x8.7x2.6 cm (€1.99) or the Holographic Shipping Box 20x13x3 cm (€3.99) is often more than sufficient.
Filling that mainly takes up space, enlarges your box. Protection that wraps around the product does so much less. A Bubble Wrap Roll 500 mm x 500 m (€12.95) allows you to tightly wrap two layers around a product instead of filling a box. For small, non-fragile items, you can often skip the box entirely: Metallic Bubble Envelopes 22x17 cm cost €0.90 each and the 33 x 23 cm variant €0.80.
4. Limit your number of box sizes, but not too much
With three box sizes, you pack faster than with ten. But if the smallest size is too big for your best-selling product, you pay that back every day. Calculate what an extra size saves you in volumetric weight, and weigh that against purchasing costs and storage space.
The mistake that ends up costing you more
Reducing volumetric weight is not a license to cram everything into the smallest possible box. A box with bulging flaps loses its sturdiness at the corners, and those corners are precisely what protects a package in a sorting center. Bulging flaps also close poorly, causing tape to come loose. A damaged shipment costs you the purchase value, shipping, return, and a customer. That weighs heavier than half a kilo of volumetric weight.
The practical minimum: there must be space on all sides for a layer of protection, the product should not press against the wall, and the flaps must lie flat on top of each other before taping them down with, for example, KINZO Packaging Tape 50 meters x 48 mm (€3.00).
Calculate it once for your own assortment
Take your five best-selling products and do this in half an hour:
Measure the outer dimensions of the box you currently send each product in.
Calculate the volumetric weight for each box: length x width x height, divided by 5000.
Next to that, note the actual weight, including packaging.
See where the volumetric weight is higher. These are your loss items.
For those products, find a size smaller or one centimeter flatter, and recalculate.
For most small webshops, the savings are found in two or three items that are packed just a little too loosely. If you switch those to a flatter format or to letterbox delivery, that will add up every week without you having to change anything else in your process.
The calculation method for volumetric weight is based on the explanation from FedEx Netherlands; the mentioned formats and weight limits come from PostNL. Rates and divisors differ per carrier and contract, so always check your own terms and conditions.
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