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In a 12×16 vs 10×20 shed, the 10×20 has 8 sq ft more floor (200 against 192), but the 12×16 is 2 ft wider inside. Pick the 12×16 for a wider aisle, a bench across the back and fewer long boards. Pick the 10×20 for long items, two work zones and more wall for shelves.

This guide compares the two sizes with numbers from the 3DSHEDPLANS plan generator and our two plan pages: the 12×16 gable shed plan with a double door and the 10×20 gable shed plan. Both are gable sheds with 94 1/2 in side walls, built on pressure-treated skids.

12×16 vs 10×20 shed at a glance

Inside sizes assume 2×4 walls, which are 3 1/2 in deep, as the American Wood Council’s lumber size chart shows for a nominal 2×4.

12×16 gable 10×20 gable
Floor area (outside of framing) 192 sq ft 200 sq ft
Inside, stud to stud about 11′ 5″ x 15′ 5″ (176 sq ft) about 9′ 5″ x 19′ 5″ (183 sq ft)
Wall length around the shed 56 ft 60 ft
Roof footprint with 8 in eaves and 4 in rakes about 13′ 4″ x 16′ 8″ (222 sq ft) about 11′ 4″ x 20′ 8″ (234 sq ft)
Overall height on our plan page, bottom of skids to peak 142 3/4 in (11′ 10 3/4″) 136 3/4 in (11′ 4 3/4″)
Doors on our plan 78 x 82 in double door (V2) or 36 in single door (V1) 78 x 82 in double door plus a 36 x 72 in side door
Rafter run at 6/12 72 in 60 in
Boards over 16 ft ridge and eave fascia, 18 ft skids, rims, wall plates, ridge and fascia, about 20 ft, all spliced

The 10×20 wins on floor, wall and roof area. The 12×16 wins on width, attic volume and fewer long boards.

Which layout fits your stuff?

Put 24 in deep shelves on both long walls and the 12×16 still leaves an aisle about 7 ft 5 in wide. The same shelves in a 10×20 leave about 5 ft 5 in, which is fine for walking but tight for turning a wheelbarrow or a mower.

The 12×16 works best when:

  • You want a workbench across the back wall and room to stand at it with the door open behind you.
  • You park something wide, like a lawn tractor with a bagger, and still want to walk around it.
  • You want more headroom under the ridge. At 6/12, the 12 ft width rises about 36 in from the wall plates to the ridge, against about 30 in on a 10 ft wide shed, so the center of the shed feels taller and a lightweight hanging rack has more room. It tapers to nothing at the eaves.

The 10×20 works best when:

  • You store long things: ladders, kayaks, lumber, a canoe or a utility trailer tongue.
  • You want two zones, such as mower parking at one end and a potting bench or small shop at the other, each with its own door.
  • You need lots of shelf run. The two long walls give about 39 ft of inside wall, against about 31 ft in a 12×16.

If you mostly need open floor in one block, the 12×16 feels bigger, even with 8 sq ft less. On a narrow side yard, remember the pad adds about 12 in on every side, so a 10×20 needs about 12 ft of clear width and a 12×16 about 14 ft before any setback.

Riding mower or tractor: which size parks better?

Both of our double-door plans use a 78 in wide by 82 in tall door. Measure your machine at its widest point, usually the deck or the bagger, then add a few inches on each side for steering.

Where the door sits changes the parking. On our 10×20 plan the double door is in the 20 ft long wall, so a mower that drives straight in has about 9 ft 5 in of floor to the back wall. On the 12×16 with the double door in the 16 ft wall, you get about 11 ft 5 in. Measure your mower nose to tail with any attachments, and leave at least 2 ft to walk past it.

For garage-style parking, with a mower, a snow blower and a cart lined up nose to tail, the 10×20 can do it only with the big door moved to a 10 ft end wall. That changes the framing (header, trimmers and end wall studs), not just the door. Our what size shed do I need guide has door widths for other equipment.

Lumber and materials: what changes

We ran both sizes through our plan generator with the same settings: 94 1/2 in walls, a 6/12 roof, 2×4 studs and rafters at 16 in on center, four 4×4 skids and a 60 in double door. These are reference builds, not the lists in either plan PDF, and the 12×16 build has one more window (two against one). The full lists are on our 12×16 shed material list and 10×20 shed material list pages.

Material 12×16 10×20
2×4 framing boards, all lengths 121 125
Extra 2x4s: braces, seam blocks, ridge post 8 12
Pressure-treated 2×6 (joists and rims) 15 21
Pressure-treated 4×4 skid pieces 4 (64 ft) 8 (80 ft)
Pressure-treated 2×4 splice scabs 0 2
3/4 in T&G plywood floor sheets 6 7
7/16 in OSB roof sheets 9 11
5/8 in T1-11 siding sheets 18 20
3-tab shingle bundles 10 11
Rafters (and hurricane ties) 26 32

Three things drive the difference:

  1. More wall. The 10×20 has 60 ft of wall against 56 ft, so more studs, plates and siding.
  2. More rafters. Rafters run across the short side. A 20 ft long roof needs 16 pairs at 16 in spacing; a 16 ft roof needs 13. Rafters on the 10×20 are shorter, though, so two come out of one 2×4 x 14 ft board.
  3. Splices. The generator’s 10×20 build splices every 20 ft run: skids (an 8 ft and a 12 ft 4×4 with treated 2×4 scabs), rim joists, wall and cap plates, the ridge and the eave fascia. The 12×16 uses 16 ft stock for skids, rims and plates; only its 18 ft ridge and fascia need splicing if your yard has no 18 ft stock.

Treated 4x4s and 2x6s in 20 ft lengths are not stocked at every lumber yard, which is why the build splices them. Spliced skids work on a level, compacted pad, but they are weak for dragging, so do not plan to tow a 10×20 to a new spot later.

What we checked: inside sizes use the 3 1/2 in actual depth of a 2×4 from the AWC chart; heights and door sizes come from our two plan pages; every count in the material table comes from our plan generator’s audited model of each build.

Cost: which one is cheaper to build?

The 12×16 usually costs a little less in materials because it has fewer pieces: 4 fewer framing 2x4s, 6 fewer treated 2x6s, 4 fewer 4×4 pieces, and one fewer sheet of plywood, two fewer of OSB, two fewer of siding and one fewer shingle bundle. The 12×16 build carries one more window, though, so compare like for like.

Our shed cost guide puts a DIY 12×16 at roughly $3,700 to $7,000 in materials, a rough estimate that varies by region and lumber prices. A 10×20 with the same finish should land a little above that. Price both lists at your own store before you decide.

The 200 sq ft line: check before you choose

Many towns base their rules on the model International Residential Code, whose section R105.2 lists one-story storage sheds of no more than 200 sq ft among work that can skip a building permit. A 10×20 is exactly 200 sq ft of floor, so it sits right on that line.

Towns do not all write the line the same way. Sherwood, Oregon, for example, lists sheds of 200 sq ft or more, or 12 ft average height or more, as needing a permit. Under wording like that, a 10×20 is over and a 12×16 is under by floor area. Some towns use lower lines, such as 100 or 120 sq ft, and zoning setbacks or HOA rules can apply at any size.

Watch the roof, too. With overhangs, the 12×16 roof covers about 222 sq ft and the 10×20 about 234 sq ft, so if your office measures the roof footprint, both are over 200. Ask where the line is, whether it reads “up to” or “under”, and whether they measure floor or roof. Our shed permit checklist covers the rest; rules vary by town, so check your local permit office.

Site and build: what to check on your lot

  • Pad size. Our 10×20 build calls for a gravel pad about 22 x 12 ft (12 in wider than the shed on every side). The same margin on a 12×16 is about 18 x 14 ft.
  • Slope. On a sloped lot, a longer shed drops more from end to end, so the low corner needs more blocking or a taller pier. Our shed foundation options guide covers skids, gravel, piers and slabs.
  • Raising walls. A 20 ft wall with studs and plates is heavy. Raise it with at least two helpers, or frame it in two sections joined with overlapping plates.
  • Squaring. Check both diagonals on the floor frame and again on the walls. On a long, narrow frame, a small out-of-square error shows up as a twisted roof line.
  • Snow. Each rafter runs 6 ft on the 12×16 against 5 ft on the 10×20, so it carries more roof. Our generator checks its 2×4 rafters at a 30 psf ground snow load; if your area gets more snow, check your local permit office for your design load.
  • Loft storage. In our builds, the 2×4 ties across the walls hold the walls together; they are not a floor. A storage loft needs its own joists sized for the load, so check your local permit office or a pro before you add one.

Common mistakes when choosing between them

  • Picking by square feet alone. The inside gap is about 7 sq ft, but the 2 ft difference in width changes every aisle.
  • Forgetting the door. A 36 in single door, like on our 12×16 single-door plan, is fine for bikes and tools but will not take a lawn tractor.
  • Assuming 200 sq ft is always under the line. It depends on how your town words and measures it.
  • Ignoring the 20 ft runs. Lumber over 16 ft is hard to find and haul, so plan the splices on a 10×20 before you order.

Plans that fit

Each 3DSHEDPLANS plan is a PDF with 3D step-by-step images, cut lengths and a full material list with quantities, priced at $19.99.

Want to look first? Download the free 12×16 double-door preview PDF or the free 10×20 preview PDF, or browse every size in our gable shed plans and shed plans collections.

Frequently asked questions

Which is bigger, a 12×16 or a 10×20 shed?

The 10×20 by 8 sq ft: 200 sq ft of floor against 192. Inside 2×4 walls the gap is about 7 sq ft, roughly 183 against 176. In daily use the shape matters more than that difference.

Is a 12×16 or 10×20 shed better for a riding mower?

Our 12×16 double-door plan and our 10×20 plan both use a 78 in double door. On the 10×20 that door is in the long wall, so a mower driving straight in has about 9 ft 5 in of floor ahead of it, against about 11 ft 5 in in a 12×16.

Is a 10×20 shed cheaper to build than a 12×16?

Usually not. In our generator builds the 10×20 takes 125 framing 2x4s against 121, 21 treated 2x6s against 15, 8 treated 4×4 skid pieces (80 ft) against 4 (64 ft), and 11 shingle bundles against 10. It also needs spliced 20 ft runs, so expect a somewhat higher materials bill.

Does a 10×20 shed need a permit when a 12×16 does not?

It can. A 10×20 sits exactly on the 200 sq ft line many towns use, and some write it as 200 sq ft or more. A 12×16 is 8 sq ft under, but its roof with overhangs covers about 222 sq ft. Rules vary, so check your local permit office.

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