Almost every week someone calls us with the same question. “I have goods ready in Guangzhou. Should I bring them by air or by sea?” The honest answer is that it depends on two things: how fast you need the goods, and how your cargo is measured. Air and sea use completely different pricing units, and once you understand them, the choice usually becomes obvious.

In short, air freight is charged per KG and sea freight is charged per CBM. The details are where people lose money, so let us walk through them.

How air freight is charged: per KG, but which KG?

Airlines sell space in a cabin that fills up long before it gets too heavy. A carton of pillows takes up the same room as a carton of engine parts, so airlines cannot charge on scale weight alone. They charge on the chargeable weight, which is the actual weight or the volumetric weight, whichever is higher.

Volumetric weight is worked out from the size of each carton:

Length x Width x Height (in cm) / 6000 = volumetric weight in KG

The 6000 divisor is the standard set by IATA for general air cargo. It works out to about 167 KG for every cubic metre. Be aware that express couriers often use 5000 instead, which makes the same carton “heavier” on paper. Always ask which divisor your quote uses before you compare two prices.

So if your goods are dense, like tiles, bolts or machine parts, you pay on actual weight. If they are light and bulky, like clothes, plastic goods or furniture, you pay on volume.

How sea freight is charged: per CBM

Sea freight works with space. A CBM (cubic metre) is simply:

Length x Width x Height (in metres) = CBM

A carton of 60 cm by 50 cm by 40 cm is 0.6 x 0.5 x 0.4 = 0.12 CBM. Multiply by the number of cartons and you have your shipment volume.

LCL: sharing a container

LCL (less than container load) means your cargo shares a container with other shippers’ goods. It is billed on what the industry calls W/M, weight or measure. One CBM is treated as equal to 1,000 KG, and you pay on whichever figure is greater. Most consolidators also have a minimum charge, commonly 1 W/M, so even a very small shipment pays for at least one CBM.

For most general goods from China, volume wins, which is why people talk about LCL “per CBM”.

FCL: your own container

FCL (full container load) means you book the whole box and pay a flat rate per container, no matter how much you put inside. A standard 20ft container has about 33 CBM of internal space and a 40ft has about 67 CBM, but in practice you should plan on loading around 25 to 28 CBM in a 20ft and 55 to 58 CBM in a 40ft once packaging and gaps are accounted for.

When does FCL make sense? When your LCL bill starts getting close to the price of a whole 20ft box. There is no fixed point, because rates move with the season, so once your cargo is getting large, ask for both an LCL and an FCL price and compare the totals, not just the freight line. FCL also means your goods are not handled alongside other people’s cargo, which helps with fragile or high value items.

Whose name is the cargo under?

With FCL, the container is imported under your own name or your company name. You pay the duty under that name, and if you are VAT registered you can later claim the VAT back. That paper trail is a real advantage for an established business.

With LCL, especially door to door shipments, the cargo is mostly imported under the consolidator’s name. The consolidator handles clearing for the whole container, which keeps things simple for small importers, but it also means the import records are not in your name. If you need to claim VAT or build an import history, talk to us about which option suits you.

Transit times: what to expect

These are typical ranges from published carrier and forwarder schedules. Your actual time depends on the origin port, the sailing or flight, and clearance.

• Sea, port to port, China to Mombasa: roughly 22 to 30 days on regular weekly services from ports like Shanghai, Ningbo and Guangzhou. Transshipment and port congestion can stretch this.
• LCL: allow extra days on top of that for consolidation in China and unpacking at a freight station in Kenya.
• Air, China to Nairobi (JKIA): typically 3 to 7 days in transit, with direct services at the faster end.

Remember to add time for pickup from the factory, customs clearance and last mile delivery on both modes.

A worked example

Please note: the rates below are made up purely to show the method. They are not quotes and not market prices.

You are importing 10 cartons of household goods. Each carton is 60 cm x 50 cm x 40 cm and weighs 18 KG.

By air

• Actual weight: 10 x 18 = 180 KG
• Volumetric weight per carton: 60 x 50 x 40 / 6000 = 20 KG
• Total volumetric weight: 10 x 20 = 200 KG
• Chargeable weight: 200 KG, because it is higher than 180 KG
• At an illustrative rate of USD 6 per KG: 200 x 6 = USD 1,200

By sea (LCL)

• Volume: 10 x 0.12 = 1.2 CBM
• Weight in tonnes: 0.18, which is lower, so you pay on 1.2 CBM
• At an illustrative rate of USD 150 per CBM: 1.2 x 150 = USD 180, plus origin, destination and freight station charges

Now change the cargo. Ten small cartons of 40 cm x 30 cm x 30 cm at 25 KG each have a volumetric weight of only 6 KG each, so air would charge on the actual 250 KG. Dense cargo narrows the gap between air and sea; bulky cargo widens it.

Clearing at Mombasa and JKIA: the basics

Whichever mode you choose, your goods still need to clear customs. In Kenya, declarations are lodged by a licensed clearing agent on the Kenya Revenue Authority’s iCMS system. You will normally need:

• Commercial invoice and packing list
• Bill of lading (sea) or air waybill (air)
• A Certificate of Conformity under the KEBS PVoC programme, if your goods fall under it
• Any permits your product needs from other agencies

On top of import duty under the EAC Common External Tariff and VAT where it applies, most imports pay an Import Declaration Fee of 2.5% and a Railway Development Levy of 2% of the customs value. Exemptions exist, so always confirm against the final assessment for your HS code.

For sea cargo, keep an eye on free days. Once they run out, shipping line demurrage and storage charges start adding up quickly.

Practical tips before you book

1. Get exact carton sizes and weights from your supplier. Guesses become invoices.
2. Ask which divisor the air quote uses, 6000 or 5000.
3. Pack smart. Oversized cartons with empty space cost you on both air and sea.
4. Compare total landed cost, not just the freight rate. Include clearing, duties, levies and delivery.
5. Split the order if it makes sense. Fly a small urgent batch and send the rest by sea.
6. Sort out PVoC early. A missing CoC can hold up cargo that has already arrived.
7. Book early before peak season, when space on both planes and ships gets tight.

Let us work out the numbers for you

Since 2009, Sidoman has been clearing and moving cargo through Mombasa and JKIA. We handle air and sea, LCL and FCL, consolidation, port to port, port to airport and door to door, right through to last mile delivery anywhere in East Africa.

Send us your carton sizes, weights and pickup city in China, and we will tell you whether air or sea makes more sense for your shipment. Get your quote today at sidoman.com.