18x21 Carport: 378 Sq Ft for One Car or Two?
CarportBay Editorial Team Last verified
An 18x21 carport is 18 feet wide and 21 feet long on the roof, which is 378 square feet. Sellers list it as a two-car size. It holds one vehicle with wide margins, and two compact cars with about two feet between them. Some sellers measure the frame at 20 feet, which gives 360 square feet.
On this page
| Attribute | Value |
|---|---|
| Width | 18 ft (216 in) |
| Length on the roof | 21 ft (252 in) |
| Length of the frame, where a seller states it | 20 ft (240 in) |
| Area | 378 sq ft by the roof; 360 sq ft by the frame |
| How sellers class it | Two-car size at Carport.com; two compact cars with little door room at Carports R Us |
| Leg heights seen in listings | 6 ft and 7 ft |
| Label variants | 18x21, 18 x 21 and, at sellers that measure the frame, 18x20 |
| Last verified | October 5, 2026 |
How big is an 18x21 carport?
An 18x21 carport measures 18 feet wide by 21 feet long on the roof, or 216 by 252 inches, which is 378 square feet of cover.
Some sellers measure the length to the frame, which is 20 ft, so the same carport reads 360 sq ft. The difference is 18 sq ft, or one foot of length across the 18 ft width.
Width decides how many vehicles fit side by side, and length decides how much room is left at the ends. The sections below work both out in inches for five named vehicles.
CarportBay's carport sizing guide lists the standard sizes and has a calculator. Sizes are also grouped as carport sizes by vehicle type, for readers who start from the vehicle.
Is an 18x21 carport a one-car or two-car size?
Sellers list an 18x21 carport as a two-car size, and the arithmetic shows it holds one vehicle with wide margins and two compact cars with narrow ones.
Every figure below is arithmetic on published vehicle dimensions and a nominal footprint, not a test by the Editorial Team. Spare length is the carport length minus the vehicle length. Side room is the carport width minus the vehicle width.
| Vehicle | Length x width x height (in) | Spare length: roof (252 in) / 20 ft frame (240 in) | Side room, total (each side if centered) | Height margin: 6 ft / 7 ft legs |
|---|---|---|---|---|
| 2025 Toyota Camry | 193.5 x 72.4 x 56.9 | 58.5 / 46.5 | 143.6 (71.8 each side) | +15.1 / +27.1 |
| 2025 Toyota RAV4 | 180.9 x 73.0 x 67.0 | 71.1 / 59.1 | 143.0 (71.5 each side) | +5.0 / +17.0 |
| 2025 Honda CR-V | 184.8 x 73.5 x 66.5 | 67.2 / 55.2 | 142.5 (71.25 each side) | +5.5 / +17.5 |
| 2024 Ford F-150 SuperCrew (67.1 in bed) | 232.0 x 79.9 (95.7 with mirrors) x 77.1 | 20.0 / 8.0 | 136.1 (68.05 each side); with mirrors 120.3 (60.15 each side) | -5.1 / +6.9 |
| 2025 Chevrolet Silverado 1500 crew cab | 231.9 x 81.2 x 75.5 | 20.1 / 8.1 | 134.8 (67.4 each side) | -3.5 / +8.5 |
Cars and SUVs
An 18x21 carport leaves 58.5 inches of spare length for a 2025 Toyota Camry and 71.1 inches for a 2025 Toyota RAV4, measured to the roof edge.
A 2025 Honda CR-V leaves 67.2 inches. Measured to a 20 ft frame, the three vehicles leave 46.5, 59.1 and 55.2 inches, so each one is more than 3 ft shorter than the carport on either reading. Lengths, widths and heights come from Edmunds specification pages for each model year, listed under Sources.
Full-size pickups
A 2024 Ford F-150 SuperCrew leaves 20.0 inches of spare length under an 18x21 roof, and 8.0 inches if you measure to a 20 ft frame.
A 2025 Chevrolet Silverado 1500 crew cab leaves 20.1 and 8.1 inches on the same two readings. Dimensions.com lists a crew cab at 241.4 inches long, which would leave 10.6 inches under the roof and put the truck 1.4 inches past a 20 ft frame. Check the length of your own truck before relying on either figure.
Two vehicles side by side
Two 2025 Toyota Camrys side by side leave 71.2 inches of width in an 18x21 carport, which is 23.7 inches for each of three gaps.
Each gap is about 2.0 ft, and it is an upper bound: the legs and frame take some of the 18 ft, and Edmunds gives a mirrors-out width only for the F-150. Door room is not rated here, because published vehicle data gives no door-swing figure.
| Pair | Combined body width | Width left over | Gap each, body only | With mirrors out |
|---|---|---|---|---|
| Two 2025 Toyota Camrys | 144.8 | 71.2 | 23.7 | Mirror width not stated |
| Two 2025 Toyota RAV4s | 146.0 | 70.0 | 23.3 | Mirror width not stated |
| Two 2025 Honda CR-Vs | 147.0 | 69.0 | 23.0 | Mirror width not stated |
| Two 2024 Ford F-150 SuperCrews | 159.8 | 56.2 | 18.7 | Total 191.4; width left 24.6; gap each 8.2 |
| Two 2025 Chevrolet Silverado 1500 crew cabs | 162.4 | 53.6 | 17.9 | Mirror width not stated |
Two 2025 Toyota RAV4s leave 23.3 inches per gap and two 2025 Honda CR-Vs leave 23.0 inches. Two F-150 SuperCrews leave 18.7 inches per gap on body width and 8.2 inches with mirrors out, which is 24.6 inches across the three gaps.
Two Camrys end to end take 387.0 inches against a 252 in roof, so a pair fits side by side only. A carport 240 in wide gives the same two Camrys 31.7 inches per gap. See 20x20 fit for two vehicles.
How much side room is there?
An 18x21 carport is 216 inches wide, so a 2025 Toyota Camry leaves 143.6 inches of total side room, or 71.8 inches on each side if centered.
Fit Checker
Pick a footprint, one or two vehicles and a leg height to see spare length, side room and height margin. The clear width between legs is a little smaller than the nominal width.
The same figures the Fit Checker reads, printed as text:
Results use published vehicle dimensions and a nominal 18x21 footprint. This is general information, not professional engineering, legal or contracting advice.
What size carport does one vehicle need?
A single-car carport needs at least 10 ft by 18 ft, and 12 ft by 20 ft is the standard size, according to Angi.
Carports R Us lists 12x20 for one car and notes that a 12 ft width gives door room on both sides. It shows the same size as 12x21 when a seller quotes the roof length, and lists 20x20 for two cars at the standard size.
| Size | Area | Named source | Camry spare length, roof | Camry side room |
|---|---|---|---|---|
| 10x18 | 180 sq ft | Angi: minimum size for one car | 22.5 in | 47.6 in (23.8 in each side) |
| 12x20 | 240 sq ft | Angi: standard size for one car | 46.5 in | 71.6 in (35.8 in each side) |
| 12x21 | 252 sq ft | Carports R Us: the 12x20 class, listed by roof length | 58.5 in | 71.6 in (35.8 in each side) |
| 18x20 | 360 sq ft | Carports R Us: two cars, tight, 360 sq ft (listed 18x20 (18x21)) | 46.5 in | 143.6 in (71.8 in each side) |
| 18x21 (this page) | 378 sq ft | Carport.com: two-car regular style, 378 sq ft | 58.5 in | 143.6 in (71.8 in each side) |
On this ladder an 18x21 carport sits at the wide end. Its 378 sq ft is 138 sq ft more than a 12x20, and a 2025 Toyota Camry leaves 71.8 inches on each side against 35.8 inches in a 12 ft width.
At the other end, a Camry in a 10x18 leaves 22.5 inches of spare length and 23.8 inches on each side. That is room for one car and little else.
The 12x20 carport page works through the standard single-car size in the same way. The 10x20 single-car footprint page covers a narrower footprint.
Why is the same carport listed as 18x20 and 18x21?
Some sellers list the same footprint as 18x20 and 18x21. Coast to Coast Carports titles one product 18x20 Two Car Carport under a URL ending 18x21, and its specification table shows a 20 ft length.
Carports R Us explains the split. Sellers usually list the roof length, which runs a foot past the frame, so a 20x21 carport has a 20 ft frame under a 21 ft roof. Its size chart lists 18x20 (18x21) at 360 sq ft as a two-car size for compact cars.
Applied here, 18 ft by 21 ft on the roof is 378 sq ft, and 18 ft by 20 ft on the frame is 360 sq ft. This is one seller's explanation and not an industry rule, so check which length a listing means before comparing prices.
Both labels describe one footprint, so Table 1 holds for either one: its two spare-length figures show the roof reading and the frame reading side by side.
The 18x20 carport page covers the same footprint under its other label.
What does an 18x21 carport cost?
List prices for 18x21 steel carports ranged from $1,595 to $3,170 on October 5, 2026, depending on seller, leg height and roof style.
| Seller and product | Listed price | Checked | Installation, as the seller states it |
|---|---|---|---|
| Garage Buildings, 18x21 Metal Buildings | From $1,595 (varies by location, wind and snow load and customization) | October 5, 2026 | Not stated on the product page |
| Central Steel Carports, 18x21 regular roof, 7 ft legs | $1,700.00 (varies by state and location) | October 5, 2026 | Free delivery and installation in 48 states, per the seller |
| Triple A Steel Structures, 18x21 regular style with one panel each side, 7 ft | $2,295.00 (starting price) | October 5, 2026 | Delivery and installation included, per the seller |
| Coast to Coast Carports, listed as 18x20 Two Car Carport, 6 ft | $2,355.00 (starting price; varies by state and customization) | October 5, 2026 | Free delivery and installation included, per the seller |
| Carport.com, 18x21 Two Car Carport Regular Style, 7 ft | $2,470.00 | October 5, 2026 | Complimentary delivery and installation, per the seller |
| Carport.com, 18x21 Two Car Carport Regular Roof, 7 ft | $3,170.00 | October 5, 2026 | Kits or professional installation, with delivery at no added cost for qualified locations, per the seller |
Divided by the 378 sq ft roof area, the six prices come to $4.22 to $8.39 per square foot. Each price is the seller's own figure on the date shown, and several sellers state that the final price varies by location or customization.
The two Carport.com rows show how much one choice can move a price: the same size and 7 ft legs cost $2,470.00 in the regular style and $3,170.00 in the regular roof. Recheck a listing before you rely on it.
Sellers also differ in who builds and installs a carport, which how carports are sold: manufacturer versus dealer lays out.
Leg height, roof and options at 18x21
An 18x21 carport is listed with 6 ft and 7 ft legs, and a 6 ft leg is lower than a 2024 Ford F-150 SuperCrew at 77.1 inches.
Table 1 measures to the leg height, which is the eave. Clearance under the roof edge is lower than the leg figure, so treat each margin as an upper bound.
A 6 ft leg is 5.1 inches lower than the F-150 SuperCrew and 3.5 inches lower than the Silverado 1500 crew cab. A 7 ft leg clears them by 6.9 and 8.5 inches, and an 8 ft leg by 18.9 and 20.5 inches. A 2025 RAV4 and a 2025 CR-V clear a 6 ft leg by 5.0 and 5.5 inches.
Sellers also vary the roof and the sides. Carport.com lists regular style and regular roof models at 7 ft, and Triple A lists a regular style model with one panel on each side at $2,295.00.
Does an 18x21 carport need a permit?
An 18x21 carport covers 378 square feet, or 360 by frame, and both are above the 200 square feet in the model International Residential Code (IRC), section R105.2, 2021 edition.
Item 1 of that section lists one-story detached accessory structures up to 200 sq ft among the work that needs no permit. Grant County, WA publishes the text, and Federal Way, WA repeats the figure. Local building departments set their own limits.
The carport is 178 sq ft above the 200 sq ft line by the roof, and 160 sq ft above it by the frame. Confirm current requirements with your local building department before beginning construction.
For the rule by location, see how carport permit rules work.
When an 18x21 is the wrong size
An 18x21 carport is the wrong size for three vehicles, for two full-size trucks that need door room, or for an RV or boat that needs a longer footprint.
Three 2025 Toyota Camrys are 217.2 inches wide together, which is 1.2 inches over the 216 in width. Two F-150 SuperCrews leave 8.2 inches per gap with mirrors out, and a carport 240 in wide leaves 26.7 inches per gap on body width.
A 12x24 carport is 288 inches long, which leaves the F-150 SuperCrew 56.0 inches of spare length against 20.0 in an 18x21. See 12x24 size and fit.
Footprints built around two vehicles are listed under two-car carport dimensions.
18x21 carport questions
One vehicle fits with wide margins, and two compact cars fit with about two feet between them. Two 2025 Toyota Camrys leave 71.2 in across three gaps, or 23.7 in each. Two F-150 SuperCrews with mirrors out leave 24.6 in across three gaps, or 8.2 in each.
Sellers list it as two-car, and Angi gives 12x20 as the standard single-car size. An 18x21 is a wide single-car size or a tight two-car size, depending on the vehicles you park in it.
An 18x21 carport is 18 feet wide by 21 feet long on the roof, which is 378 square feet. Some sellers measure the frame at 20 feet, which is 360 square feet, or 18 square feet less.
At least 10 feet by 18 feet, with 12 feet by 20 feet the standard size, according to Angi. A 2025 Toyota Camry leaves 22.5 in of spare length in a 10x18 and 58.5 in in an 18x21.
Often one foot of listed length and 18 square feet. Some sellers list the same footprint under either label: Coast to Coast titles a product 18x20 under a URL ending 18x21, and its specification table shows a 20 ft length.
Yes for a 2024 Ford F-150 SuperCrew, with 20.0 inches of spare length under the roof and 8.0 inches over a 20 ft frame. Check the leg height too: a 6 ft leg is 5.1 inches lower than the truck.
It depends on your local rule. At 378 square feet it is above the 200 square feet in the model International Residential Code, section R105.2, 2021 edition. Confirm current requirements with your local building department before beginning construction.
List prices seen on October 5, 2026 ran from $1,595 to $3,170, and the price table names each seller and date. Several sellers state that the final price varies by location or customization.
Next steps: build it yourself or have it installed
Before choosing an 18x21 carport, enter your vehicle in the Fit Checker and compare the roof and frame lengths in each listing.
If you prefer to install it yourself, compare 18x21 carport kits and the makers behind them.
Four of the six sellers in the price table state that delivery and installation are included, and this page on how to have a carport delivered and installed covers the steps.
Sources
Vehicle dimensions come from the Edmunds pages named below, prices from seller product pages, and the permit figure from the code text and a city page. All were read on October 5, 2026.
- Edmunds, 2025 Toyota Camry: Camry length, width and height.
- Edmunds, 2025 Toyota RAV4: RAV4 length, width and height.
- Edmunds, 2025 Honda CR-V: CR-V length, width and height.
- Edmunds, 2024 Ford F-150 SuperCrew: F-150 length, width, width with mirrors and height.
- Edmunds, 2025 Chevrolet Silverado 1500 crew cab: Silverado length, width and height.
- Dimensions.com, Silverado 1500 Crew Cab: the second length reading for the crew cab.
- Angi, carport sizes: single-car and two-car sizes, updated July 8, 2026.
- Carports R Us, carport size guide: roof length versus frame length, size chart, modified September 23, 2026.
- Coast to Coast Carports, 18x20 Two Car Carport: title, URL and specification length, price.
- Carport.com, 18x21 Two Car Carport Regular Style: 18 ft by 21 ft by 7 ft, 378 sq ft, price, updated April 6, 2026.
- Carport.com, 18x21 Two Car Carport Regular Roof: price.
- Garage Buildings, 18x21 Metal Buildings: starting price and 378 sq ft.
- Central Steel Carports, 18x21 Regular Roof Steel Carport: price and installation statement.
- Triple A Steel Structures, 18x21 Regular Style Carport: price and installation statement.
- IRC 2021 section R105.2, Grant County, WA: 200 sq ft exemption, Building item 1.
- Federal Way, WA, residential permit exemptions: 200 sq ft exemption.
Last verified: October 5, 2026
Last verified: October 2026. Each price row shows its own date.