Volumetric weight: how couriers bill you, and how a smaller box cuts the bill

Couriers do not really sell weight. They sell space in a van or in an aircraft hold.

It works like a berth on a train. A thin passenger and a heavy passenger pay the same fare, because each of them occupies one berth.

Here is the short answer. The courier calculates the volumetric weight of your parcel: length × breadth × height in centimetres, divided by a fixed number called the divisor. For most express services in India, the divisor is 5000. You are billed on the volumetric weight or the actual weight, whichever is higher, rounded up to the next slab.

For most light products, the carton decides the bill, not the product inside it.

We make tapes, films and paper packaging in Jaipur, not courier rate cards. I cannot give you rates, because every contract is different and rates change often. What I can give you is the method, because packaging is our business and the packed carton is exactly what the courier measures.

Below, we go through the divisors couriers publish and end with a calculation you can repeat with your own numbers.

How is volumetric weight calculated?

Let us take it in three steps.

1. Measure the packed parcel from the outside: length, breadth and height, in centimetres.
2. Multiply the three and divide by the courier's divisor. At 5000, a 40 × 30 × 20 cm box is 24,000 cm³ ÷ 5000 = 4.8 kg.
3. Weigh the parcel. The higher of the two weights, rounded up to the courier's slab, is your chargeable weight. Amazon.in, for example, uses 500 g steps.

Keep one thing in mind when you compare couriers.

A smaller divisor makes the same carton heavier on paper.

Which divisor does each courier use?

We took these from each courier's own published terms, and we checked every page on 2 October 2026.

Is your courier or shipping aggregator missing from this table? Then ask them for the divisor and the slab size in writing.

Both are part of your rate agreement, and both change the bill as much as the rate per kg does. I would read those two lines before I read the rate.

Why can surface shipping count your box heavier than air?

Let us look again at the Blue Dart surface rule. 10 kg for every 27,000 cm³ is the same as a divisor of 2,700.

So the same carton counts almost twice as heavy on surface as on air express.

A 40 × 30 × 25 cm carton is 6.0 kg at ÷ 5000. On the surface rule, it is 11.1 kg.

Surface rates per kg are lower, which is the whole reason anyone books surface, and once you work out the charge per parcel it may well still be the cheaper service for you. But compare the two services on the charge per parcel, never on the rate per kg. For bulky, light goods, the rate per kg alone will point you to the wrong service.

Does box size matter for your product? A one-minute density check

Not always, and here is a quick check you can do yourself.

Divide the packed weight in kg by the box volume in litres. To get litres, divide the cm³ by 1,000.

1. Above 0.2 kg per litre, the actual weight is the higher one at a 5000 divisor. The box size will not change your courier bill. Work on the actual weight instead.
2. Below 0.2 kg per litre, volumetric weight decides. Every centimetre you take off can save money.
3. On a surface service billed at 10 kg per cubic foot, the line moves up to about 0.37 kg per litre. At the air cargo divisor of 6000, it moves down to about 0.17.

Think of a carton of books next to a carton of cushions. The books are well above the line. The cushions are far below it.

I like this check because it needs only a scale, a measuring tape and one minute of arithmetic.

How should you measure a parcel?

Assume the courier will measure your parcel from the outside, at its widest points, after it reaches them. Measure it the same way, with the same dimensions, before it leaves your warehouse.

1. Measure the outside of the carton, not the inside. A corrugated box is bigger outside than inside by two wall thicknesses in each of its three dimensions.
2. Measure after packing and taping. An overfilled box bulges, and the bulge is part of the size.
3. Ask your dispatch supervisor to weigh and measure 10 packed parcels of each best seller. Note the largest figures, not the average. I would also keep a photograph of each parcel next to the measuring tape.
4. Declare the size you measured. A size that is too small on paper can come back later as a weight dispute and an extra charge.

How each courier handles a disagreement about dimensions is a contract question, so read that clause in your agreement before you sign.

Seven ways to cut volumetric weight

1. Stock a few carton dimensions that fit your best sellers. One large box for every order is convenient, and it is expensive.
2. Cut the shortest side first. On a 45 × 30 × 15 cm carton, 3 cm off the 15 cm side removes a fifth of the volume. The same 3 cm off the 45 cm side removes only one fifteenth.
3. Use a courier bag or mailer for products that do not need a box, such as clothes and soft goods. On Delhivery's published rule, flyers are charged on dead weight up to 1 kg.
4. Ship in the product's own retail box if it is strong enough. A box inside a box adds two extra walls and the air between them. Test this before you do it.
5. Use cushioning that protects in less space. Five centimetres of loose fill on every side adds 10 cm to each dimension of the carton.
6. Fold, nest or flat-pack products where the design allows it.
7. Put a multi-item order into one right-sized carton instead of two separate parcels. Two parcels each pay their own first slab.

Here is one warning about slabs.

A smaller carton saves money only when the chargeable weight drops into a lower slab. If 2.9 kg and 2.6 kg both bill as 3.0 kg, that extra squeeze bought you nothing.

Aim for the slab line, not just for "smaller".

What if the actual weight is the higher one?

Then box size is not your lever. The weight of the packaging is.

Check whether the carton grade is heavier than the product needs, and whether the inserts and the void fill add grams that do no protective work at all. Thinner films and tapes help a little too, as we explain in our guide to downgauging.

I will be honest here. For a dense product, the packaging is usually a small share of the total weight, so these savings are small. Do not spend months on them. Fix the light, bulky products first.

If you export

The same logic applies, with different divisors. DHL Express uses 5000. General air cargo uses 6000, as per the IATA rule above.

We export to 20+ countries, so this is arithmetic we do for our own shipments too.

By sea, you pay for container space, so the carton plan matters more than the weight of any one carton. A carton that is 1 cm smaller on each side can change how many fit on a pallet, and how many pallets fit in a container.

Do not shrink the box until the product breaks

A snug box leaves less room for cushioning. Save ₹40 of freight on a parcel, replace an ₹800 product, and you are ₹760 worse off.

I would rather pay one slab more than send a customer a broken delivery and a replacement.

Before you switch, pack a few orders the new way and drop-test them. Then put a number on what one broken delivery costs you. Our worksheet on what a damaged delivery really costs shows how.

Your calculation

Here is the method we suggest. Put your own figures in place of ours.

Every figure in this example is an ASSUMPTION, chosen only to show the arithmetic. None of them is a courier's rate or our price.

1. Product: a set of steel kitchen containers in its own retail box. Packed weight 1.6 kg (assumed).
2. Courier: divisor 5000, 500 g slabs, ₹30 for each extra 500 g (assumed).
3. Volume: 900 parcels a month (assumed).

The density check: 1.6 kg ÷ 14.6 litres is 0.11 kg per litre. That is below 0.2, so volumetric weight still decides, even in the snug carton.

Now assume the snug carton costs ₹5 more per piece, because it is a custom size. The net saving is ₹175 per parcel.

At 900 parcels, that is ₹1,57,500 a month.

Notice how close the snug carton sits to the line. At 3.04 kg, it would bill as 3.5 kg and lose one slab of saving. When a design lands just above a slab, take one more centimetre off the shortest side.

To repeat this in a spreadsheet, keep one row per product:

1. Volumetric weight: = L × B × H ÷ divisor
2. Chargeable weight: = ROUNDUP(MAX(actual, volumetric) ÷ slab, 0) × slab
3. Slabs saved: = (old chargeable − new chargeable) ÷ slab
4. Monthly saving: = (slabs saved × rate per extra slab − extra box cost) × parcels per month

I would start with your five highest-volume products, because a slab saved there repeats on every order.

Start with today's dispatch. Measure 10 parcels of your best seller and do the density check. It will take you less time than this article did.