CBM Calculator: The Short Answer
A founder has 50 cartons of hoodies measuring 60 × 40 × 40 centimetres and a freight quote priced per cubic metre. The CBM calculator multiplies length, width and height in centimetres and divides by a million: each carton is 0.096 CBM, and the 50 cartons come to 4.8 CBM. With 60 pieces in each carton that is 3,000 hoodies, or 625 pieces per CBM. If the forwarder quotes a rate per CBM, the freight bill is that rate multiplied by the chargeable volume, so the number you have just worked out is the one to check on the quote.
CBM means cubic metre, the unit shipping lines use for the volume of cargo. For garments, which are bulky but light, volume is usually what decides the freight bill, so carton size and how tightly you pack matter as much as the number of pieces. A CBM calculator is therefore one of the most useful tools a buyer can keep to hand: it lets you check a freight quote, compare two carton designs and plan a booking, all from numbers you can measure on the table in front of you before production is finished.
Use the CBM Calculator for Clothing Cartons
Enter the outside dimensions of one carton in centimetres, the number of cartons and, if you know them, the pieces and gross weight per carton. The CBM calculator returns the volume of a carton, the total for the shipment, the pieces per CBM and a note on the chargeable volume for LCL sea freight. If you have a freight quote per CBM, add it and the calculator estimates the freight and the cost per piece.
CBM calculator for clothing cartons
Cubic metres, pieces per CBM and chargeable volume
CBM is the volume of the carton, not what fits in a container. Real loading is lower because of pallets, gaps and stacking limits. Container capacities are approximate internal volumes.
The container table shows what share of each container size your cartons would occupy by volume. It is a quick sanity check, not a loading plan: real containers rarely fill to their full volume. Our container loading calculator for clothing cartons works out how many cartons of your size actually fit.
How to Calculate CBM by Hand
The arithmetic is short enough to do on a phone. Measure the outside of the packed carton, not the garments, because the carrier charges for the space the carton takes. Multiply length by width by height in centimetres, divide by 1,000,000, then multiply by the number of cartons.
From carton size to shipment CBM
- 1Measure the cartonLength, width and height in cm, outside, as packed.
- 2MultiplyLength × width × height gives cubic centimetres.
- 3Convert to CBMDivide by 1,000,000 to get cubic metres.
- 4Multiply by cartonsCBM per carton × number of cartons = total CBM.
- 5Check the weightCompare with the gross weight in tonnes for LCL charging.
If your measurements are in inches, multiply length, width and height in inches and multiply by 0.000016387 to convert cubic inches to cubic metres. Round the carton measurements up to the next centimetre, because carriers may re-measure, so your estimate is less likely to be lower than theirs.
CBM per Carton for Common Sizes
The table shows the CBM of five carton sizes that are common for folded garments, with the number of cartons that make up one cubic metre and the volume of a hundred cartons. It makes it easy to see how a few centimetres on one side change the freight bill.
CBM for typical carton sizes
| Carton size (cm) | CBM per carton | Cartons per CBM | CBM for 100 cartons |
|---|---|---|---|
| 50 × 40 × 30 | 0.060 | 16.7 | 6.00 |
| 60 × 40 × 40 | 0.096 | 10.4 | 9.60 |
| 60 × 40 × 50 | 0.120 | 8.3 | 12.00 |
| 70 × 50 × 40 | 0.140 | 7.1 | 14.00 |
| 80 × 60 × 50 | 0.240 | 4.2 | 24.00 |
Calculated as length × width × height ÷ 1,000,000. Illustrative sizes; your cartons may differ. Cartons per CBM is theoretical and ignores gaps.
Going from a 60 × 40 × 40 carton to a 60 × 40 × 50 carton raises each carton by 0.024 CBM, a rise of 25%. If the extra height is empty space inside the carton, you are paying freight on air. Right-sizing cartons to the garments is one of the cheapest freight savings available, and it begins with the CBM calculator.
Chargeable Volume: CBM or Weight?
Sea freight for part loads, known as LCL, is normally priced on the greater of the volume in CBM and the weight in tonnes, with one CBM treated as equal to one tonne. For garments, the volume is almost always greater, because a cubic metre of cartons weighs far less than a tonne. Air freight works differently, converting volume to a volumetric weight and charging the greater of that and the actual weight, which our volumetric weight calculator for clothing cartons explains.
Share of a 20ft container's volume taken by the 4.8 CBM example
- The 50 example cartons (4.8 CBM)14.5%
- Remaining capacity (28.4 CBM)85.5%
Illustrative arithmetic using an approximate 33.2 CBM internal volume for a 20ft container. Real loading capacity is lower than full volume.
The pie shows why a small shipment rarely justifies a whole container: the example takes about a seventh of a 20ft container by volume. You pay freight on carton volume whether it holds garments or air, so polybags, folding method and carton choice change the CBM, the freight cost per piece and the share of a container you need.
From CBM to Freight Cost per Piece
Once you have the CBM, the freight cost is a simple multiplication, and the cost per piece follows from the pieces per CBM. The table shows the 4.8 CBM example at four illustrative rates per CBM, so you can see how sensitive the cost per piece is to the quote. The rates are placeholders for the arithmetic, not market prices.
Freight on 4.8 CBM and 3,000 pieces at illustrative rates per CBM
| Illustrative rate per CBM | Freight on 4.8 CBM | Freight per piece |
|---|---|---|
| £60 | £288 | £0.10 |
| £80 | £384 | £0.13 |
| £100 | £480 | £0.16 |
| £120 | £576 | £0.19 |
Illustrative arithmetic: rate × 4.8 CBM, divided by 3,000 pieces. The rates are placeholders, not quotes; use your forwarder's current rate.
Per-piece freight is small compared with the garment, which is why many buyers pay it little attention until volumes grow. But freight is only one line, and it comes with port and handling charges on both ends, so ask the forwarder what is included in the rate. The CBM calculator gives you the number you need to ask the right question, and the result belongs in your landed cost.
Which Container Does Your CBM Fit?
A full container load, or FCL, is priced per container, not per CBM, so it makes sense to compare your volume with the container capacities. Internal volumes are approximately 33 CBM for a 20ft container, 68 CBM for a 40ft container and 76 CBM for a 40ft high cube, although the exact figure varies a little by container and manufacturer. Container sizes are standardised internationally, with the ISO publishing the relevant standards.
Approximate internal capacity of common containers
Cubic metres
Approximate internal volumes from published container specifications. Usable capacity is lower once cartons, gaps and stacking limits are taken into account.
As a rule, once your shipment is a large fraction of a 20ft container by volume, it is worth asking your forwarder for an FCL quote, because the per-CBM LCL rate carries a premium for consolidation. Our guide to sea freight versus air freight for clothing compares the two options.
Reducing the CBM of a Clothing Order
Freight savings often come from the carton, not the garment. A few changes to how an order is packed can reduce CBM without changing a single stitch, and they cost little to specify before production begins.
Ways to reduce CBM
- Fit carton size to the folded garments so there is little empty space
- Fold consistently and use a size that stacks without gaps
- Choose a carton dimension that divides neatly into container width
- Use polybags that compress rather than rigid inserts
- Avoid mixing sizes in cartons that waste volume
- Confirm the carton specification before packing starts
Practical ideas. Garment protection and handling must not be compromised, so agree changes with your supplier.
Once you know the CBM, use it, and keep it with the order so every later freight conversation starts from the same number. Divide your freight quote by the pieces to find the freight cost per piece with the shipping cost per garment calculator, and carry it into your landed cost. Forwarders and their trade body FIATA can advise on options for your route.
How Ruhrose Helps You Plan Cartons
Ruhrose develops hoodies, fleece, jersey, denim and woven casualwear for UK buyers, with production in Bangladesh. We can discuss carton sizes and pieces per carton during development, so you know the CBM before the order is packed, not after the freight quote lands. See Ruhrose's clothing manufacturing pages for what we make, and bring your target landed cost to the conversation.
Before your next order, ask yourself one question: do you know the CBM of your cartons well enough to check a freight quote?