What this tool does
Couriers bill on the greater of a parcel's actual weight and the space it occupies, so a box full of air can cost more to ship than a dense one of the same weight. The second number is volumetric weight and it is a single division: length times width times height in centimetres, divided by a divisor that depends on the carrier. The number of divisors published online, and the direction several sites apply them in, is where most sellers get it wrong. This tool shows the divisor it used, computes the chargeable weight on the correct billing slab, and converts to CBM for freight forwarders.
How it works
The formula is (L x W x H in cm) divided by the divisor, and the divisor is the only variable. 5000 is the Indian domestic courier standard used by Delhivery, Blue Dart, DTDC and XpressBees, and it is also the divisor DHL, FedEx, UPS and TNT apply on express. 6000 is the IATA air freight standard. 4500 and 4750 appear on some Indian domestic streams and 4000 on certain surface and LTL contracts. The same box can therefore be billed at 12 kg or 15 kg purely on the carrier, so the divisor belongs in the calculation rather than in a general rule of thumb.
Several calculators publish these the wrong way round, labelling 6000 as the courier figure and 5000 as the air freight figure, or treating the number as a multiplier when it is a divisor. The imperial column has the same trap: 139 in3/lb is the twin of 5000, used by UPS, FedEx and DHL Express international, and 166 in3/lb is the twin of 6000, used for IATA air and USPS. A larger divisor always produces a smaller chargeable weight, so confusing the two understates air freight by a fifth and overstates courier freight by the same margin.
Chargeable weight is the larger of the two weights, then rounded up to the billing slab. Couriers bill in 0.5 kg or 1 kg increments, so 1.8 kg becomes 2.0 kg on a 0.5 kg slab and 2 kg on a 1 kg slab. Rounding to the nearest value rather than up is a small error that recurs on every parcel, and it is the difference between a rate card that reconciles against the invoice and one that does not.
Sea freight changes the shape of the rule rather than the divisor. LCL shipments are billed on W/M, whichever is greater of weight in tonnes or volume in cubic metres, because a container of polystyrene uses more space than its mass justifies. 1 CBM is 1,000,000 cm3, which is 35.3147 cubic feet, and at the standard 1 CBM = 1,000 kg the forwarder rule of thumb is that air and LCL cost about the same per CBM. Working in CBM also tells a seller whether a larger master carton is worth the price break it triggers on a quantity break.
Worked example
A parcel measures 30 x 20 x 15 cm and weighs 0.9 kg. Billed on the Indian domestic courier divisor of 5000.
- Volume = 30 x 20 x 15 = 9,000 cm3
- Volumetric weight = 9,000 / 5,000 = 1.8 kg
- Actual weight of 0.9 kg is lower, so chargeable weight = 1.8 kg
- Rounded up to a 0.5 kg slab = 2.0 kg, or 2 kg on a 1 kg slab
- CBM = 9,000 / 1,000,000 = 0.009 CBM
- Cross-check: 60 x 40 x 40 cm / 5,000 = 19.2 kg, and the same box / 6,000 = 16 kg
The courier bills 2.0 kg, not 0.9 kg, because the parcel is charged on the air inside it. A 60 x 40 x 40 cm box swings from 19.2 kg to 16 kg on the divisor alone.
Accuracy and limitations
- Divisors vary by carrier, service level and contract, and couriers change them. Confirm the figure in your rate card rather than relying on any published default.
- Billing slabs are set per courier, not globally. 0.5 kg and 1 kg slabs both exist, some carriers apply a different minimum to the first kilogram, and a couple bill volumetric weight to the next whole kilogram only.
- Multi-piece shipments are usually assessed on the sum of the pieces rather than the cube of the outer carton, which can change which of the two weights ends up chargeable.
Frequently asked questions
- What divisor does volumetric weight use in India?
- 5000 for Indian domestic courier (Delhivery, Blue Dart, DTDC, XpressBees) and for DHL, FedEx, UPS and TNT express, and 6000 for IATA air freight. Some Indian domestic carriers use 4500 or 4750, and some surface and LTL contracts use 4000, so confirm against your own rate card.
- What is the volumetric weight of a 30 x 20 x 15 cm parcel?
- 1.8 kg on the 5000 divisor, because 30 x 20 x 15 = 9,000 cm3 and 9,000 divided by 5,000 = 1.8. The same box is 1.5 kg on the 6000 air divisor, and either way you are billed on the larger of that and the actual weight.
- Is volumetric weight higher or lower than actual weight?
- It depends on how dense the parcel is. Dense goods such as metal, glass or hardware weigh more than they measure, so the actual weight wins. Light and bulky goods such as pillows, void fill or a small appliance in an oversized box measure more than they weigh, so the volumetric weight wins and the air is what you pay for.
- Why is my volumetric weight lower than another site's?
- Almost always the divisor, or which side of the division it is on. A larger divisor gives a smaller weight, so air freight at 6000 is lighter per cubic metre than courier at 5000. Some sites also multiply by the divisor instead of dividing, or paste a per-kilogram rate where the divisor should be.
- What is CBM and how do I convert to it?
- CBM is cubic metres of freight space. 1 CBM equals 1,000,000 cm3 and 35.3147 cubic feet. In LCL sea freight it is billed on W/M, the greater of tonnes and cubic metres, with 1 CBM conventionally treated as 1,000 kg.
- Do I measure the outer carton or the item?
- Use the outer carton as packed, because that is what the courier measures and bills. Cutting void fill and moving to a closer-fitting box is the cheapest freight saving available to a seller, since the chargeable weight falls with the cube and not with the contents.