What the Dimensional Weight Calculator does
This calculator works out the volumetric (dimensional) weight of a parcel from its length, width and height, compares it with the actual weight, and tells you the chargeable weight - the larger of the two, which is what couriers bill. It handles centimetres or inches, kilograms or pounds, several boxes at once, and the divisors the main carriers publish.
Volumetric weight exists because a large, light parcel takes up space on a van or plane that a small, heavy one does not. Choose your carrier's divisor, or type the one on your rate card, and the page shows each step of the rounding. The divisors are a dated reference table; nothing is sent to any carrier.
How to use it
- Choose centimetres or inches and kilograms or pounds, then enter each box's length, width, height and weight. Measure the longest points, including any bulge.
- Add more boxes for a multi-piece shipment and set how many of each there are.
- Pick the divisor your courier uses: 5,000 for international express (DHL Express and most express couriers), 139 for FedEx and UPS US rates, USPS for its parcels over one cubic foot, or 6,000 for air cargo - or choose Custom and enter the figure from your rate card.
- Read the chargeable weight. The warning tells you when a box is billed for empty space and the largest box that would keep it at its real weight.
- Optionally enter your price per kg or lb for a rough cost, and compare the same shipment under every divisor in the table below.
Reading the results
If the volumetric weight is higher, you are paying for the space the parcel takes up. A smaller box, less void fill or a different service can make a large difference - a cushion parcel billed at 12 kg weighs only 2.5 kg.
If the actual weight is higher, the box is dense and the size does not matter; shrinking it saves nothing on the weight charge.
Couriers bill each piece separately, so the shipment total is the sum of every box's chargeable weight, not the volumetric weight of all boxes added together and compared once.
A lower divisor means a higher volumetric weight: the same box is heavier at 4,000 than at 5,000, and heavier at 5,000 than at 6,000.
Worked example: a light parcel of cushions sent by express courier
The box is 50 x 40 x 30 cm and weighs 2.5 kg. Its volume is 50 x 40 x 30 = 60,000 cm3.
With the international express divisor of 5,000, volumetric weight is 60,000 / 5,000 = 12 kg. Chargeable weight is the larger of 12 kg and 2.5 kg, so the parcel is billed as 12 kg - about 79% of what you pay for is empty space.
To be billed at its real 2.5 kg the box would need to be no bigger than 2.5 x 5,000 = 12,500 cm3, for example 25 x 25 x 20 cm. Sent as air cargo at 6,000 the same box would be 10 kg.
Formulas and scoring rules
- Volumetric weight (metric)
kg = length_cm x width_cm x height_cm / divisor5,000 is the common international express divisor (200 kg per cubic metre); 6,000 is the standard air-cargo ratio.- Volumetric weight (imperial)
lb = length_in x width_in x height_in / divisor139 is the divisor FedEx, UPS and USPS publish for US parcels. 1 in = 2.54 cm exactly; 1 lb = 0.45359237 kg exactly.- Chargeable weight
chargeable = max(actual_weight, volumetric_weight)Both weights are first rounded up to the carrier's billing step - usually 0.5 kg for express or a whole pound in the US.- Rounding of dimensions
side = ceil(side) when the carrier rounds upUSPS rounds each measurement up to the next whole inch; FedEx and UPS round fractions of an inch up as well. Express rules in centimetres are applied to the measured sizes.- USPS threshold
if length x width x height <= 1,728 in3, bill actual weightUSPS applies dimensional weight only to parcels over one cubic foot.- Largest box for a target weight
max_volume = target_weight x divisor- Multi-box shipment
total = sum over boxes of chargeable_each x quantity
Where the divisors come from
USPS publishes its rule in the Domestic Mail Manual: round each side up to a whole inch, and if the volume exceeds 1,728 cubic inches divide by 139 and round up to the next pound. DHL Express states its formula as length x width x height in centimetres divided by 5,000. FedEx and UPS use 139 for their published US rates and round fractions of an inch up; their pages could not be read automatically when this table was reviewed, so those figures were cross-checked against several industry reports and you should confirm them on the carrier's site. The air-cargo ratio of 6,000 cm3 per kg is the standard IATA volume ratio used by forwarders.
Indian domestic couriers publish their own volumetric rules on their rate cards, and they differ by service - air express, surface and part-truck-load can each use a different divisor. Use Custom and enter the figure your courier quotes.
Limitations: what the result does not prove
- Divisors and rounding change and depend on your account, service and country. The table records the published list rules on its review date; your contract or rate card always wins.
- It does not price the shipment. Fuel surcharges, remote-area fees, oversize and additional-handling charges, minimum billable weights and pallet rules are not included.
- Irregular shapes are measured as the box that would contain them. Couriers measure the longest, widest and highest points, so a bulging box is bigger than its nominal size.
- The cost line is a simple multiplication of chargeable weight by the rate you enter; real tariffs are usually stepped by weight band and zone.
Privacy: where your data goes
Everything you paste, type or drop is processed in this browser tab. It is not uploaded, logged, stored or sent to analytics. Session recording and tag-manager scripts are switched off on this page.
Standards and sources
- USPS Domestic Mail Manual 253 - dimensional weight for parcels over one cubic foot
- DHL Express - Weight and dimensions (volumetric weight)
- FedEx - What is dimensional weight?
- UPS - Shipping dimensions and weight
Frequently asked questions
How do you calculate volumetric weight in kg?
Multiply length, width and height in centimetres and divide by the courier's divisor, usually 5,000. A 40 x 30 x 20 cm box is 24,000 cm3, so its volumetric weight is 24,000 / 5,000 = 4.8 kg, billed as 5 kg if the courier rounds up to half kilograms.
What is chargeable weight?
It is the weight a courier actually bills: the larger of the parcel's actual weight and its volumetric weight, each rounded up to the billing step. A 12 kg volumetric box that weighs 2.5 kg is charged as 12 kg.
What dimensional weight divisor does FedEx use?
For published US rates FedEx, like UPS, divides cubic inches by 139 and rounds up to the next pound. International express services are generally quoted at 5,000 cm3 per kg. Negotiated accounts can have a different divisor, so check your contract.
Why is my parcel charged more than it weighs?
Because it is large for its weight, so its volumetric weight is higher than the scale weight and the courier bills the space it takes. Use a smaller box or less packing; the page shows the largest box that would be billed at the real weight.
Is 5,000 or 6,000 the volumetric divisor?
Both are in use. 5,000 cm3 per kg is common for international express couriers; 6,000 is the standard air-cargo ratio used by freight forwarders. A lower divisor gives a higher volumetric weight, so the same box costs more at 5,000.
Does USPS charge dimensional weight on small boxes?
No. USPS applies dimensional weight only when a parcel's volume is over 1,728 cubic inches, which is one cubic foot. Smaller parcels pay by actual weight. Above it, the volume is divided by 139 and rounded up to the next pound.
How is volumetric weight worked out for several boxes?
Each box is assessed on its own: work out its chargeable weight, multiply by how many there are, and add the boxes together. Two 35 x 25 x 20 cm boxes of books at 9 kg each plus a 60 x 30 x 30 cm lamp box at 4 kg come to 9 + 9 + 11 = 29 kg at a 5,000 divisor.
Last reviewed by the A2Z.Tools team against the sources listed above.
