Size Is the First Decision, and the Hardest to Undo
You can change finishes, fixtures, and layouts halfway through a container build. You cannot change the box. The size you buy sets your ceiling height, how the kitchen and bathroom fit, what delivery costs, and whether your plan meets the local minimum size for a dwelling. Here is how the three common sizes compare for living in, rather than for storage.
The Numbers Side by Side
- 20-foot standard: about 19'4" long, 7'8" wide, and 7'10" tall inside, or roughly 150 square feet. Used units run about $1,500 to $3,000.
- 40-foot standard: about 39'6" long, 7'8" wide, and 7'10" tall inside, or roughly 300 square feet. Used units run about $1,800 to $3,200.
- 40-foot high cube: the same footprint as the standard 40-foot but about 8'10" tall inside, one foot more. Used units run about $2,200 to $3,800, and one-trip units about $4,000 to $7,000.
Every size shares the same limit that matters most: roughly 7'8" of interior width before insulation. After spray foam and finished walls, expect about 7'2" to 7'4", which shapes every layout decision.
Why Ceiling Height Matters More Than Length
A standard container's 7'10" sounds adequate until you build inside it. Insulating the ceiling, adding a subfloor, and running wiring and ducts can take 6 to 10 inches. That leaves a standard container close to the 7-foot minimum ceiling height for habitable rooms in most residential codes, and noticeably cramped. The high cube's extra foot gives room for proper insulation, recessed lighting, a ducted range hood, and a ceiling that feels like a room instead of a box. For a small 10 to 20 percent premium on a line that is only a small part of the total budget, it is the easiest upgrade in the whole project.
The 20-Foot Container: Best as a Studio, Office, or Cabin
At about 150 square feet, a 20-foot container fits a sleeping area, a compact wet bath, and a kitchenette, and not much else. It is easier to deliver on a standard tilt-bed truck to tight sites, and it shines as a backyard home office, a weekend cabin, or a guest room. As a full-time home for more than one person it is very tight, and its per-square-foot cost is the highest of the three, because a bathroom costs the same whatever its size. 20-foot high cubes exist but are much less common than 40-foot ones, so check availability before you plan on the extra height.
The 40-Foot Standard: The Budget Trap
A 40-foot standard gives you real length for separate zones, and it is often the cheapest container per square foot on the lot. But it has the same ceiling problem as the 20-foot across twice the floor area. Owners who save a few hundred dollars on the box often regret it every day they live under a low ceiling. Choose it only when a high cube is truly unavailable or when the unit will not be lived in full time.
The 40-Foot High Cube: The Default for Living
This is what most container home builders use, for good reason. Its roughly 320 square feet fit a proper bedroom, a full bathroom, a galley kitchen, and a living area in one line, and its height makes insulation and mechanical work far easier. Its main drawbacks are delivery, since a 40-foot unit needs a long, clear approach and sometimes a crane, and the fact that 320 square feet may still fall under a local minimum size for a primary dwelling. See our 40-foot layout walkthrough for how the space breaks down.
When to Combine Containers
Two 40-foot high cubes placed side by side with the shared walls cut out give about 640 square feet and a room width of about 15 feet. That solves the narrowness problem and many minimum-size rules at once. It also brings engineered steel for the removed walls and a roof seam that must be flashed perfectly. It is a bigger project, but it is often the one that gets approved as a primary home.
Our Pick
- Office, studio, or occasional cabin: 20-foot, or a 40-foot if the site allows
- Full-time home for one or two people: one 40-foot high cube
- Family home or strict minimum-size zoning: two or more 40-foot high cubes
- Avoid for full-time living: the 40-foot standard, unless the lower ceiling truly does not bother you
Related Reading
- How Much Does It Cost to Convert a Shipping Container Into a Home?
- 7 Things to Check Before Buying a Shipping Container
- Are Shipping Container Homes Legal? Permits, Zoning, and Building Codes
See the complete build in the shipping container to guest house guide, and compare sizes by budget with the cost calculator.