Shipping Weight Calculator

Couriers and freight companies don’t just weigh a parcel. They also work out a “volumetric” or “dimensional” weight from its size, and bill whichever is higher. A pillow in a big box weighs little but fills a van, so it is priced as if it were heavy. This calculator shows both figures side by side, the chargeable weight that wins, and how much of your bill is paying for empty space.

Pick a carrier and the right divisor is filled in for you: 5,000 cm³ per kg or 139 in³ per lb for UPS, FedEx and DHL Express, USPS’s rule that changed on 12 July 2026, UPS retail rates, Australian cubic weight at 250 kg per cubic metre, and the usual air and sea freight rules. Or type the figure from your own contract. Add as many boxes as the shipment holds, set how many of each, and choose whether the carrier rounds up and whether it charges box by box or on the whole consignment.

When a box is billed on size, the tool tells you the largest box that would be billed on weight instead, and what trimming a couple of centimetres off each side would save. Your carrier’s own quote is always final.

1. Choose “cm and kg” or “inches and lb”, then pick your carrier or service. Choose “Custom divisor…” to enter your own.
2. Type the length, width, height and weight of the first box, and “How many” if you are sending several the same.
3. Press “Add a box” for each different box in the shipment. The cross on a box removes it.
4. Open “Rounding and billing” to round up to the next 0.5 or whole kilo or pound, round sides to whole units, or charge on the whole shipment.
5. Read “You’ll be charged for”, the box-by-box table and “Ways to pay less”. Press “Copy summary” to paste the numbers into an email or quote.

• Six carrier presets checked in October 2026, plus a custom divisor in cm³ per kg, in³ per lb or kg per m³.
• Centimetres and kilograms or inches and pounds; switching units converts the boxes you have typed.
• Any number of boxes, each with a quantity, and totals for volume, real weight and volumetric weight.
• Billing per box, as parcel couriers do, or on the whole shipment, as air and sea freight usually do.
• Rounding options: weights up to the next 0.5 or 1 kg or lb, and sides up to whole centimetres or inches. US presets switch on the carriers’ inch and pound rounding for you.
• USPS’s 1 cubic foot threshold: smaller parcels are charged on real weight only.
• Bars that compare real and volumetric weight at a glance, and a table showing which one sets each box’s price.
• Box-size advice for every parcel billed on size, with a copyable summary.

• Measure the longest point of each side, including bulges, handles and loose tape.
• Light, bulky goods like clothes, cushions and lampshades are where volumetric weight bites. A padded mailer or satchel that hugs the item often costs far less than a box.
• Ordering boxes? Keep two or three sizes that fit your best sellers snugly rather than one big size for everything. Empty space is billed, and void fill costs money too.
• Business accounts often get a better divisor than counter rates, such as 139 instead of 166 at UPS. Ask your carrier which figure your contract uses and enter it as a custom divisor.
• Freight quotes usually add a minimum charge per consignment, fuel surcharges and fees for oversized or very heavy pieces. This tool works out weight, not price.