How many CBM fits in a 20GP and a 40GP?

20GP interior is approximately 5.90m × 2.35m × 2.39m for a theoretical 33.2 CBM; real-world load is 25-28 CBM (75-85% packing efficiency). 40GP interior is 12.03m × 2.35m × 2.39m, 67.7 CBM theoretical, 55-60 CBM real. 40HQ interior is 12.03m × 2.35m × 2.70m, 76.4 CBM theoretical, 65-68 CBM real. Real-world load depends on carton fit, stacking strength, and lashing space.

What is the maximum payload of a 20GP, and why does it weigh out before cubing out?

20GP tare is ~2.2 tons; carrier MGW typically 30.48 tons (28 tons net payload). China road regulation (GB 1589) limits trucking to ~22-24 tons including the container, so effective net cargo is ~22 tons. High-density cargo (stone, metal, machinery) hits the weight ceiling well before the CBM ceiling — the industry phrase is 'load weight, not volume'.

How much bigger is 40HQ than 40GP, and why do shippers prefer 40HQ?

40HQ is 31cm taller inside than 40GP (2.70m vs 2.39m), adding 8-9 CBM. Ocean freight cost is essentially the same — typically USD 50-150 difference. For volumetric cargo (garments, furniture, toys), 40HQ is always the better economics. 40GP is only used when cargo height is limited (machine notch height) or destination cannot truck 40HQ.

How do I calculate CBM and decide between LCL and FCL?

CBM = length(m) × width(m) × height(m). A 30 × 20 × 15 cm carton is 0.009 CBM. LCL is priced per CBM (USD 80-150/CBM on US/EU lanes); FCL is priced per container. Rules of thumb: ≤14 CBM → LCL; 15-25 CBM → depends on lane and timing; ≥25 CBM → 20GP; ≥50 CBM → 40GP; ≥60 CBM → 40HQ. Heavy cargo follows weight rather than CBM — 20GP can be full at 22-24 tons / 12-15 CBM.

Container Sizes & Load Calculation: How Much Fits in 20GP / 40GP / 40HQ / 45HC?

Q: Why is packing efficiency rarely 100%?

Real loading loses space due to: (1) cartons not perfectly dividing into container dimensions; (2) corrugated steel walls reduce actual usable width by 2-3 cm; (3) 5-10cm of top space unusable because of door height; (4) carton stacking strength caps the number of tiers (typically 6-8); (5) dunnage, airbags, and lashing materials take space. A real 85-92% efficiency on 40HQ is already good. Pre-loading in Excel or CBM Calculator software typically finds 3-5 more CBM.

One-line takeaway

Over 95% of international ocean container cargo moves in four standard boxes: 20GP, 40GP, 40HQ (High Cube), 45HC. Box selection really answers two questions: will it fit, and can it be trucked? Fitting is about CBM and packing efficiency (75-92%); trucking is about China road law (GB 1589, effective ~22-24 tons including container) and the carrier's Maximum Gross Weight (MGW). The economic combination: 20GP for heavy cargo, 40HQ for light cargo, 45HC for oversized light cargo.

1. Standard container size reference

Type	External (L×W×H)	Internal (L×W×H)	Door (W×H)	Capacity	Tare	MGW
20GP	6.06 × 2.44 × 2.59 m	5.90 × 2.35 × 2.39 m	2.34 × 2.28 m	33.2 CBM	~2.2 t	30.48 t
40GP	12.19 × 2.44 × 2.59 m	12.03 × 2.35 × 2.39 m	2.34 × 2.28 m	67.7 CBM	~3.8 t	30.48 t
40HQ (High Cube)	12.19 × 2.44 × 2.90 m	12.03 × 2.35 × 2.70 m	2.34 × 2.58 m	76.4 CBM	~3.9 t	30.48 t
45HC	13.72 × 2.44 × 2.90 m	13.56 × 2.35 × 2.70 m	2.34 × 2.58 m	86.1 CBM	~4.8 t	30.48 t

* Industry-typical figures. Actual dimensions vary slightly by carrier, age, and manufacturer. Confirm with the carrier's EIR / Container Specification at booking.

2. What you can really load

The gap between theoretical and real-world capacity catches new shippers out. Packing efficiency = actual CBM loaded ÷ theoretical capacity. Industry typicals:

Type	Theoretical	Typical real load	Efficiency	Recommended use
20GP	33.2 CBM	25-28 CBM	75-85%	Heavy / dense cargo
40GP	67.7 CBM	55-60 CBM	81-89%	Medium density
40HQ	76.4 CBM	65-68 CBM	85-92%	Volumetric / extra height needed
45HC	86.1 CBM	73-78 CBM	85-92%	Oversized light, US inland

Loss factors:

Carton dimensions rarely divide cleanly into container dimensions — gaps remain
Corrugated steel inner walls reduce usable width by 2-3 cm
Top 5-10cm unusable due to door-height clearance
Stacking tiers capped by carton crush strength (typically 6-8 tiers)
Lashing, dunnage, airbags, anti-slip materials all take space

3. CBM and packing-count formulas

Per carton volume: CBM = L(m) × W(m) × H(m)

Cartons per container: divide each container dimension by carton dimension, take the integer, then multiply.
Example — carton 60 × 40 × 30 cm into 40HQ (interior 1203 × 235 × 270 cm):

Option A: 60 lengthwise → 1203 ÷ 60 = 20; 40 widthwise → 235 ÷ 40 = 5; 30 heightwise → 270 ÷ 30 = 9 tiers. Total = 20 × 5 × 9 = 900 cartons, 64.8 CBM
Option B: 40 lengthwise → 30; 60 widthwise → 3; 30 heightwise → 9. Total = 30 × 3 × 9 = 810 cartons, 58.3 CBM

Same cartons, Option A loads 90 more boxes (+11%). Loading orientation determines packing efficiency. Ten minutes in Excel or a CBM calculator before stuffing typically gains 5% or more.

4. LCL vs FCL tipping points

The eternal question: "Is this enough cargo for FCL?"

Volume	Recommended mode	Reason
≤14 CBM or ≤6 t	LCL	LCL priced per CBM, cheaper for small volumes
15-25 CBM	Borderline LCL vs 20GP FCL	Compare destination LCL rate, transit time, security preference
25-50 CBM	20GP FCL	Exclusive container, faster clearance
50-60 CBM	40GP FCL	Medium-density cargo
60-68 CBM	40HQ FCL	Volumetric cargo's first choice
68-78 CBM	45HC FCL (US lanes)	Common for US ocean+truck and ocean+air
≥78 CBM	Multiple FCL	2 × 40HQ or 2 × 40GP

* Heavy cargo (stone, metal) follows weight rather than CBM. A 20GP can be "full" at 22-24 tons and 12-15 CBM.

5. Weight limits: MGW, payload, road regs

Three commonly confused "max weights":

Term	Definition	Typical
MGW (Max Gross Weight)	The container's design max combined weight (tare + cargo)	20GP / 40GP / 40HQ all 30.48 t
Payload	MGW − tare	20GP ~28 t, 40HQ ~26.5 t
Carrier limit	Carrier's own restriction (may be tighter)	20GP 26-28 t, 40HQ 26-27 t
China road limit	GB 1589 plus local overload enforcement	20GP ~22-24 t, 40HQ ~24-26 t (incl. container)
Destination road limit	US ~21.7 t (48,000 lbs) / EU 24 t / AU 25 t	Often tighter than China

Key insight: "carrier allows 28 tons" does not mean you can load 28 tons. The China road limit is the actual bottleneck. Loading 20GP to 28 tons is fine on the vessel, but the first weighbridge en route from factory to port will stop you with a fine and forced offload. Before loading, confirm: (1) destination road limit; (2) origin trucking limit; (3) carrier limit. Take the lowest.

5.1 VGM (Verified Gross Mass)

Mandated by SOLAS from July 2016: every export container must have a Verified Gross Mass filed before loading or the carrier refuses to load. Two methods:

Method 1: weigh the loaded container at a certified weighbridge — works for any cargo
Method 2: sum-up calculation (cargo + packaging + pallets + lashing + container tare) — for standardized cartonized cargo

VGM is submitted by the shipper before the carrier's VGM cutoff, which is typically 24-48 hours earlier than the SI cutoff. Discrepancy > ±5% vs the actual gross weight on the B/L can trigger USD 200-1,000 in penalties per shipment.

6. Special container selection

Type	Abbr.	Suitable cargo	Typical size / capacity	Key considerations
Open Top	OT	Over-height (machinery, sculptures, tanks)	20OT / 40OT, top opens for crane loading	Needs tarpaulin + wood bracing; overheight billed as heavy lift
Flat Rack	FR	Over-width / over-length (steel structures, wind blades)	20FR / 40FR, no side walls	OOG cargo billed as Flat Rack
Reefer	RF	Frozen / chilled / temp-controlled	20RF / 40RH (HQ reefer)	Insulation steals 4-5 CBM vs GP; PTI test report required
Tank	TK	Liquid chemicals, food-grade liquids, oils	20TK, 17-26,000 L	Must meet UN tank standards; DG declares via IMDG
Ventilated	VC	Coffee beans, cocoa, hides — "breathing" agri-products	20VC, side vents	Mainly SE Asia / Africa lanes
Garment on Hanger	GOH	Finished garments (suits, dresses)	40HQ with hanging rails	Lower CBM efficiency than cartons but no ironing at destination
Side Door	SD	Large machinery, long items	40HQ-SD, full-side opening	Same capacity as 40HQ but easier load/unload

7. Nine loading best practices

Centered center-of-gravity: heavy cargo on bottom; left-right weight near symmetric (front-back differential ≤60% of container tare).
Floor protection: place plastic pallets or cardboard between cartons and steel floor to prevent condensation damage.
Stack limit: follow the carton-printed "stacking tiers" (typically 5-8). Over-stacking crushes the bottom.
Carton-row reinforcement: strap the bottom row; use airbags or stretch film on top to prevent shift.
Load in reverse of unload order: last in, first out. With multiple consignees per box, group cargo by consignee.
Packing list inside: the original packing list in a plastic sleeve taped inside the door for destination inspection.
Door clearance: leave 20-50cm before the door for inspection; use an airbag at the last row to prevent migration during transit.
IPPC compliance: all wood packaging (pallets, crates) must carry the IPPC mark (HT heat-treated or MB methyl bromide). No mark = destination destruction or return.
Photo evidence: 6 photos during loading (empty box interior, mid-load, fully loaded, labeling, sealing, closed door with container/seal number close-up) — your strongest evidence in damage disputes.

8. Six common loading pitfalls

Case 1 · 20GP overweight, forced offload: loaded 26 t of stone (carrier allows 28 t) but China road limit is 22 t. First weighbridge stopped the truck; 4 t was offloaded and sent in a separate container. Result: vessel missed + extra freight cost.
Case 2 · Over-height cargo in 40GP: furniture samples 245cm tall, but 40GP interior height is 239cm. Forced sideways loading, severe damage. Should have used 40HQ (270cm).
Case 3 · OT tarp leaks: open-top with machinery covered by old tarp — sea-spray penetrated and rusted the equipment. OT tarps must be new or verified intact, with an LOI confirming inspection.
Case 4 · Wood pallets without IPPC mark destroyed: Australia-bound machinery on un-fumigated pallets — destroyed by AU customs + AUD 2,000 fine + demurrage. All wood packaging needs IPPC treatment.
Case 5 · Lopsided container tips the chassis: 40HQ loaded with heavy machinery on one side and empty cartons on the other — the chassis tipped on a turn. Always balance left-right and front-back.
Case 6 · VGM cutoff missed, container rolled: carrier's VGM cutoff lapsed without submission — container rolled to next vessel; freight already paid was not refunded; rebooking required. Add VGM cutoff to the loading calendar.

9. Freight & transit time reference (ex Qingdao)

Type	LA (US West)	NY (US East)	Rotterdam (N. Europe)	HCMC (SEA)	Sydney (AU)
20GP	USD 2,200-3,500	USD 3,800-5,500	USD 2,500-4,000	USD 600-1,200	USD 1,800-3,000
40GP	USD 3,200-4,800	USD 5,500-7,800	USD 3,800-5,500	USD 900-1,800	USD 2,500-4,200
40HQ	USD 3,300-4,900	USD 5,600-7,900	USD 3,900-5,600	USD 950-1,850	USD 2,600-4,300
Transit	12-18 days	30-45 days	30-40 days	5-10 days	20-28 days

* Indicative only. Rates swing significantly with season, BAF/PSS, and capacity. Contact us for live quotes.

10. How Mighty International can help

With 26 years at Qingdao port, our ocean operations team offers:

Container selection & load planning — free CBM calculation + load diagram
Booking for 20GP / 40GP / 40HQ / 45HC ex Qingdao, Shanghai, Ningbo, Shenzhen
Special containers (OT / FR / RF / TK / GOH) via 30+ direct carrier relationships
SOC (shipper-owned containers) including lithium-battery DG
Supervised loading and photo log across all Qingdao terminals
VGM filing via certified weighbridges — SOLAS-compliant
IPPC fumigation for wood packaging

Not sure which container?

Send us the commodity, units, carton dimensions, and weight — we will come back within an hour with a container recommendation and load plan.

Talk to us

Frequently asked questions

How many CBM fits in 20GP and 40GP?

20GP theoretical 33.2 / real 25-28; 40GP theoretical 67.7 / real 55-60; 40HQ theoretical 76.4 / real 65-68. Real load depends on carton fit, stacking, and lashing.

What is the max payload of 20GP, and why does it weigh out first?

MGW 30.48 t, net ~28 t — but China road law limits to ~22-24 t. Dense cargo (stone, metal) weighs out before cubing out — "load weight, not volume."

How much bigger is 40HQ than 40GP, and why prefer 40HQ?

40HQ is 31cm taller inside, +8-9 CBM, but freight is only USD 50-150 different. For volumetric cargo it's always better economics.

How do I calculate CBM and decide LCL vs FCL?

CBM = L × W × H (meters). Rules of thumb: ≤14 CBM LCL; 15-25 CBM borderline; ≥25 CBM 20GP; ≥50 CBM 40GP; ≥60 CBM 40HQ.

Why is packing efficiency rarely 100%?

Cartons don't divide cleanly; walls have corrugations; door height steals top space; stacking strength caps tiers; lashing material takes room. 85-92% on 40HQ is already good. Pre-loading in Excel usually finds 3-5 more CBM.

References & further reading

ISO 668: Series 1 freight containers — Classification, dimensions and ratings
SOLAS Chapter VI / Regulation 2 — VGM mandate (effective July 2016)
GB 1589-2016 — China vehicle and load dimensional / mass limits
IPPC ISPM 15 — International Standards for Phytosanitary Measures for Wood Packaging
Related guides: Bill of Lading Types & Handling, DDP Shipping from China

Disclaimer: General informational content. Specific container dimensions, weight limits, and operational requirements defer to the carrier's published Container Specification and current regulations.