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Raised bed calculator

Enter the size of the bed and the boards you want to use. We draw it, cut every board from the lengths the store sells, count the screws and the soil, and price what we have read at the store.

A 8'-0" by 4'-0" bed, 0'-11" tall, takes 4 2x6 boards, 6 treated 4x4 posts and 44 screws. It holds 23.8 cu ft of soil; order 27.4 cu ft (1.0 cu yd) with 15% for settling. Wood, screws, topsoil and compost come to $214.06 at the store.
Top view: 8'-0" by 4'-0" outsideSide view: 2 x 2x6, 0'-11" tall, posts dashed
Drawn to scale from your numbers. Dark squares are the 4x4 posts, the yellow band the 2x4 tie across the top.
Cut list
PartLumberLengthPieces
Long side boards2x68'-0"4
End boards, between the long sides2x63'-9"4
Corner and side posts4x40'-11"6
Top tie across the middle2x44'-0"1
What to buy. Boards are cut so the offcuts are as small as the store lengths allow.
ItemQtyEachTotal
2x6 x 8 ft pressure-treated, ground contact8'-0"; 8'-0"2$9.68$19.36
2x6 x 16 ft pressure-treated, ground contact8'-0" + 3'-9" + 3'-9"; 8'-0" + 3'-9" + 3'-9"2$19.48$38.96
4x4 x 8 ft pressure-treated, ground contact0'-11" + 0'-11" + 0'-11" + 0'-11" + 0'-11" + 0'-11"1$10.78$10.78
2x4 x 8 ft pressure-treated, ground contact4'-0"1$4.88$4.88
Exterior #9 x 3 in screws, box of 309 (44 needed)1$32.97$32.97
Topsoil, 1 cu ft bag (the 60% topsoil part)17$2.87$48.79
Compost, 1 cu ft bag (the 30% compost part)9$6.48$58.32
Pine bark fines or perlite, 2.7 cu ft-not priced yetnot priced yet
Soil mix to order
16.4 cu ft topsoil, 8.2 cu ft compost, 2.7 cu ft bark fines or perlite
Bagged raised bed soil instead
19 bags of 1.5 cu ft at $9.98 = $189.62, in place of the topsoil, compost and bark fines
Topsoil in bulk instead
$48.95 at $80.50 a cu yd, before delivery
Inside size
7'-9" by 3'-9"
Posts
6 at 0'-11", no more than 4 ft apart along each side

Prices are shelf prices at The Home Depot, Hamilton Mill store, before tax: treated lumber read Oct 8, 2026, DECKMATE #9 x 3 in screws read Nov 4, 2026, Vigoro 1 cu ft topsoil read Nov 6, 2026, and 8 cu. yd. Bulk Screened Topsoil read Nov 6, 2026. Black Kow 1 cu ft compost and Miracle-Gro 1.5 cu ft raised bed soil are shelf prices at Lowe's Atlanta-Edgewood, read Nov 12, 2026. Bark fines are not priced yet, so they are not in the total.

Filling a bigger area? Topsoil calculator

Cubic yards, tons and bags of topsoil for lawns and beds of any shape.

Building figures from common practice and extension service guidance, not a structural design. Store prices are shelf prices at one store and change; check yours before you buy.

Common raised bed sizes

Worked out with the calculator above, treated pine.
BedHeightBoards to buySoil to orderStore costWith cedar
4x4 ft, 2 boards of 2x60'-11"2 x 16 ft13.2 cu ft$131.59$228.57
4x8 ft, 1 board of 2x100'-9"1 x 8 ft and 1 x 16 ft22.6 cu ft$184.83not priced yet
4x8 ft, 2 boards of 2x60'-11"2 x 8 ft and 2 x 16 ft27.4 cu ft$214.06$355.66
4x8 ft, 3 boards of 2x61'-5"3 x 8 ft and 3 x 16 ft42.4 cu ft$300.77$513.17
3x6 ft, 2 boards of 2x81'-3"1 x 8 ft and 2 x 16 ft19.8 cu ft$183.31$400.99
4x12 ft, 2 boards of 2x60'-11"4 x 16 ft41.6 cu ft$286.04$494.00
4x16 ft, 2 boards of 2x81'-3"5 x 16 ft75.3 cu ft$490.09$921.66

Store cost is the treated lumber, the screws, and the topsoil and compost parts of the mix; bark fines are not priced yet. The cedar column swaps the side boards for cedar (posts stay treated); 2x10 and 2x12 cedar are not priced yet.

How the bed goes together

A treated 4x4 post stands inside each corner. The long side boards run the full length and the end boards fit between them, so every board is screwed into a post: 2 screws per board end on a 2x6, 3 on a 2x8 or 2x10. A long side gets another post at least every 4 ft, because wet soil pushes the boards out. Over 6 ft long, a 2x4 tie across the top keeps the middle from bowing.

Width and length

4 ft wide is the usual limit, since you can reach the middle from either side without stepping in. Against a fence or a wall, keep the bed nearer 3 ft. Length is up to you: past 16 ft the long boards meet over a middle post, and the calculator cuts them that way.

Filling it

Fill to about 1 in below the top. A common mix is about 60% screened topsoil, 30% compost and 10% coarse material such as pine bark fines. Bags make sense for one or two beds; for more, a load of bulk topsoil is cheaper and fewer trips. For a border or a whole garden, the topsoil calculator and the mulch calculator take any shape.

Where the numbers come from

Treated lumber, screw and topsoil prices are shelf prices read at The Home Depot, Hamilton Mill store, the same readings the deck and pergola plans use. Cedar boards, bagged compost and bagged raised bed soil are shelf prices read at Lowe's Atlanta-Edgewood on Nov 12, 2026. The building rules (post spacing, ties, screws per board, fill depth and the soil mix) are common builders' and extension service practice, marked editorial wherever they show. No building code covers a garden bed.

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Questions

Anything else? Write to us or see every calculator.

Questions people ask

A 4x8 bed built from two 2x6 boards stands 0'-11" tall and holds about 23.8 cu ft once filled to 1 in below the top. With 15% extra for settling and a mix of about 30% compost, that is 8.2 cu ft of compost, next to 16.4 cu ft of topsoil.

Two boards high in 2x6: 2 x 8 ft and 2 x 16 ft boards, plus 6 4x4 posts cut to 0'-11". Each long side takes a full 8 ft board per row, and the end pieces are cut two to a board, so nothing over 8 ft is needed. Wood, screws, topsoil and compost for it come to $214.06 at the store with treated pine, or $355.66 with cedar side boards.

Most vegetables do well in 10 to 12 in of loose soil, which is two 2x6 boards (0'-11"). Lettuce, herbs and flowers manage with 6 to 8 in; carrots, potatoes and tomatoes like 12 to 18 in. Over poor or compacted ground, go three boards high (1'-5") or loosen the soil under the bed (editorial; extension service guidance varies by region).

Multiply the inside length by the inside width in feet to get square feet, then by the soil depth in inches divided by 12 to get cubic feet. Divide by 27 for cubic yards. A 4x4 bed two 2x6 boards high is about 11.4 cu ft inside, so order 13.2 cu ft with extra for settling.

Lumber sold for homes since 2004 is treated with copper compounds (ACQ, CA or MCA), not the older CCA with arsenic. Many extension services consider it acceptable for food beds, and some still suggest a liner or cedar for peace of mind. The calculator prices both treated pine and cedar so you can compare (editorial).