A 20-foot container measures 19 ft 10.5 in outside, and a 40-foot container measures a true 40 ft 0 in outside. Width holds at 8 ft 0 in on both, and height is 8 ft 6 in on the standard boxes or 9 ft 6 in on a 40-foot high cube. Every figure below is Ocean Network Express's own published dry container specification, read 2026-08-31.
The steel walls take about seven inches off the length and four off the width between the outside footprint and what actually fits inside.
Three sets of numbers describe a container's size: the outside footprint that decides what fits on a chassis or a ship's cell guide, the inside cavity that decides what cargo actually fits, and the door opening that decides what can be walked or forklifted through the end of it. The table below pulls all three for a 20 ft, a 40 ft and a 40 ft high cube dry container.
| Container | Outside (L × W × H) | Inside (L × W × H) | Door opening (W × H) |
|---|---|---|---|
| 20 ft standard | 19'10.5" × 8'0" × 8'6" 6,058 × 2,438 × 2,591 mm | 19'4" × 7'8.5" × 7'10" 5,898 × 2,350 × 2,390 mm | 7'8" × 7'6" 2,340 × 2,280 mm |
| 40 ft standard | 40'0" × 8'0" × 8'6" 12,192 × 2,438 × 2,591 mm | 39'5.5" × 7'8.5" × 7'10" 12,032 × 2,350 × 2,390 mm | 7'8" × 7'6" 2,340 × 2,280 mm |
| 40 ft high cube | 40'0" × 8'0" × 9'6" 12,192 × 2,438 × 2,896 mm | 39'5.5" × 7'8.5" × 8'10" 12,032 × 2,350 × 2,695 mm | 7'8" × 8'6" 2,340 × 2,585 mm |
The gap between outside and inside length runs about six to seven inches on every size — the thickness of the corrugated steel end walls plus the corner castings that let containers stack and lock to a chassis. The gap on width and height is smaller, since the side walls and roof carry less structure than the door end.
19 ft 10.5 in outside is the actual figure Ocean Network Express publishes for its 20 ft equipment. The "20-foot" and "40-foot" labels describe the nominal size class every carrier and port builds around, not a promise of an exact 20-foot or 40-foot tape reading.
A 40-foot container's outside length comes in at a true 40 ft 0 in — no rounding needed. The shortfall on the shorter box and the exact match on the longer one both come from the same fixed corner-casting hardware; it simply reads as a smaller share of a 40-foot length than a 20-foot one.
Every dry container in this table shares the same 8 ft 0 in outside width, because width is what decides whether a container fits a ship's cell guide, a rail well car and a highway lane. Only length and height change between the classes.
A 40-foot high cube keeps the same 40 ft 0 in outside length and 8 ft 0 in outside width as a standard 40-footer. The only change is a full extra foot of height — 9 ft 6 in outside instead of 8 ft 6 in — which passes straight through to the inside: 8 ft 10 in of interior height against 7 ft 10 in, and a door opening that grows from 7 ft 6 in to 8 ft 6 in.
Inside dimensions decide how a load is planned — pallet counts across the width, coil or machinery clearance against the door opening, whether a piece that is 39 feet 8 inches long will physically go in a 40-foot box (it will not; the true inside length is 39 ft 5.5 in). Outside dimensions decide how the empty container itself is handled: what fits on a chassis, what a crane's spreader locks onto, and what a port or rail yard counts against its stacking envelope. Weight is a separate question entirely — how much the empty box weighs and how much cargo it is rated to carry by weight, not size, is covered in SMKlog's shipping container weight guide, sourced from the same Ocean Network Express spec sheet.
None of that is a price. A container move is quoted by a person against the ports, the commodity, the packed weight and the ready date. This page answers one narrower question: how big the box actually is, outside and in.
ONE's spec sheet prints an explicit outside-dimension row for its reefer, flat-rack and open-top equipment on the same page, but not for the dry line itself. Its 20 ft reefer and flat-rack outside figures (6,058 × 2,438 × 2,591 mm) and its 40 ft and 40 ft high cube flat-rack and reefer outside figures (12,192 × 2,438 × 2,591/2,896 mm) match the 8'6"/9'6" labels ONE attaches to the dry line at each length, which is expected: every ISO-family container of the same nominal length and height class shares one exterior footprint and the same corner castings, dry or otherwise, so it can stack and lock the same way. That is the source for the outside column above. ISO 668, the international standard that sets container classification and external dimensions, was also checked on iso.org on 2026-08-31; its dimension tables sit behind ISO's own access controls and every page tried returned a block, so this page relies on Ocean Network Express alone rather than guessing at the ISO figures.
Container lines revise their equipment sheets without notice, and an individual box can run slightly off a published nominal figure depending on its manufacturer, age and repair history. Treat the table above as representative of a current standard steel dry container from one carrier's equipment pool.
A 20-foot container runs 19 ft 10.5 in outside, and a 40-foot container runs a true 40 ft 0 in outside — both figures published by Ocean Network Express for its 20 ft and 40 ft equipment, read 2026-08-31. The "20-foot" and "40-foot" names describe the nominal class, not a guaranteed exact length.
One foot of height. A standard 40 ft dry container is 8 ft 6 in tall outside; the high cube version is 9 ft 6 in tall outside, adding a full 12 inches to both the interior height and the door opening height, per Ocean Network Express's published specifications, read 2026-08-31.
19 ft 4 in long, 7 ft 8.5 in wide and 7 ft 10 in tall inside, according to Ocean Network Express's dry container specifications, read 2026-08-31. That is roughly six inches shorter than the outside length once the corrugated steel walls and corner castings are accounted for.
7 ft 8 in across on every dry container length Ocean Network Express publishes — 20 ft, 40 ft and 40 ft high cube share the same door width. Door height is 7 ft 6 in on the standard boxes and 8 ft 6 in on the high cube, per the same spec sheet, read 2026-08-31.
That is a separate question from length and width. See SMKlog's shipping container weight guide for the tare, payload and maximum gross weight of the 20 ft, 40 ft and 40 ft high cube boxes covered here.