Order of work
- Pick a level spot in full sun, close to a hose. Call 811 (in the US) a few days before you dig post holes, so buried lines get marked.
- Clear the ground. On lawn, mow short and strip the sod or plan to cover it with cardboard; loosen the soil underneath with a garden fork so roots and water can go deeper.
- Cut the boards and posts following the cut plan. The long walls use full-length boards; the short walls fit between them.
- Build each frame on a flat surface: screw the boards to the corner posts with their tops flush and the post ends sticking out below, then add the posts along the long walls. Check that the diagonals are equal so the bed is square.
- Add the bottom. For hardware cloth, flip the frame, staple the mesh to the bottom edges of the boards and notch it around the posts.
- Set the frame: dig a hole for each post, drop the frame in so the bottom boards sit on the ground, level it along both walls and pack the soil back around the posts. On lawn, lay overlapping cardboard inside now.
- Fill and water: mix the topsoil and compost as you fill, soak it, and top it up as it settles over the first weeks.
- Plant and water about 1 in a week in summer; raised beds dry out faster than the ground, so check them more often in hot spells.
Tools you’ll need
- Circular saw or miter saw, and a speed square
- Drill/driver or impact driver with a bit for the screws
- Tape measure, pencil and a 4 ft level
- Post-hole digger or a narrow spade
- Heavy-duty stapler and tin snips (for hardware cloth)
- Wheelbarrow, shovel and garden fork
- Gloves, safety glasses and hearing protection
About this planner
A raised bed is a simple box, but its shopping list isn’t: boards cut to length for every course, posts at the corners and along the long sides, the right screws, something underneath to stop grass or gophers, and far more soil than most people expect. This planner works all of it out for one bed or a whole garden, prices every line, compares bagged soil with a bulk delivery, and draws the layout, a corner section and a board-by-board cut plan to scale.
It follows university extension guidance: beds no wider than 4 ft so you can reach the middle, a post at least every 6 ft of wall, posts twice the bed height with half in the ground, and a fill of topsoil blended with compost.
How to use it
- Enter the length and width of one bed, outside to outside, and the number of beds. Keep beds 4 ft wide or less so you never have to step in them.
- Pick the height. Each option is a stack of standard boards, so the planner knows exactly what to cut.
- Choose the wood, what goes under the bed, and how to buy the soil: “whichever is cheaper” compares bags with a bulk delivery at your prices.
- Open Your local prices, enter your store’s prices, then print the project sheet with the cut plan.
How the quantities are worked out
Height = courses × board width (2×6 = 5½ in, 2×8 = 7¼, 2×10 = 9¼, 2×12 = 11¼)
Each course = 2 long boards (full length) + 2 short boards (width − 3 in)
Posts per bed = 4 corners + enough along each wall that no span is over 6 ft
Post length = 2 × bed height, half of it in the ground
Screws = 2 per board end at every post (3 for 2×10 and 2×12)
Board feet = feet of board × (2 × nominal width ÷ 12): 1 per foot of 2×6
Soil = (inside length × inside width − posts) × height × beds × 1.15
Bulk = topsoil and compost, each rounded up to the ½ cu yd, + 1 delivery
Water per week = growing area × 1 in = 0.62 gal per sq ft
Sources: bed width, path widths and post length (twice the bed height) from University of Missouri Extension (G6985); reinforcing walls longer than 6 ft or taller than about 18 in from Oregon State University Extension (FS 270); the soil mix (⅔ to ½ topsoil, the rest compost) from University of Minnesota and University of Maryland Extension; about 1 in of water a week from University of Minnesota Extension; ½ in hardware cloth against gophers from UC IPM. Board sizes follow the American Softwood Lumber Standard (PS 20). The cut plan packs the pieces into 8–16 ft boards with the least waste, allowing ⅛ in for each saw cut, and picks the shorter board when the waste is about the same. The 15% extra for settling matches our topsoil calculator.
Worked example
These are the planner’s starting values and the results they produce:
| Bed length | 8 ft |
|---|---|
| Bed width | 4 ft |
| Bed height | 11 in – two 2×6s |
| Number of beds | 2 |
| Path between beds | 2 ft |
| Wood | Cedar or redwood (rot-resistant, costs more) |
| Under the bed | Open to the soil (cardboard over grass) |
| Buy the soil | Whichever is cheaper |
| Bulk mix | ⅔ topsoil, ⅓ compost |
| Soil bag size | 1.5 cu ft bag |
| Boards, per board foot | $2.50 |
| 4×4 × 8 ft post, each | $22.00 |
| Hardware cloth, per sq ft | $0.80 |
| Bulk topsoil, per cu yd | $35.00 |
| Bulk compost, per cu yd | $40.00 |
| Bulk delivery fee | $75.00 |
| Bagged raised-bed soil, per bag | $10.00 |
| Bought | Item | Buy | Cost |
|---|---|---|---|
| Boards, cedar 2×696 board feet, cut into 8 × 8' and 8 × 3' 9" (see the cut plan) | 12 × 8 ft | $240.00 | |
| 4×4 posts, cedar, 8 ftcut into 12 × 22 in: 6 per bed (4 corners + 2 along the sides), half in the ground | 3 | $66.00 | |
| Exterior screws, 3 in2 per board end at every post | 80 | — | |
| Plain cardboard, tape removedoverlapped under each bed to smother grass (skip on bare soil) | 64 sq ft | — | |
| Screened topsoil, bulk1.49 cu yd needed, rounded up to the ½ yd | 1.5 cu yd | $52.50 | |
| Compost, bulk0.74 cu yd needed, rounded up to the ½ yd | 1 cu yd | $40.00 | |
| Bulk deliveryask for a split load or a ready-mixed garden blend | 1 load | $75.00 | |
| Estimated materials total | $473.50 | ||
Tips before you buy
- Sight down each board before you buy it; twisted or bowed boards make a crooked bed.
- Use exterior screws. For pressure-treated lumber they must be rated for it (hot-dip galvanized, coated for treated wood, or stainless), because the copper in the treatment corrodes plain steel.
- The posts go into the ground, so use cedar or ground-contact treated posts even when the walls are pine.
- Ask the soil supplier for a ready-mixed garden blend or a split load of topsoil and compost, so you pay one delivery fee.
- Leave paths at least 2 ft wide if you’ll bring a wheelbarrow; 1 ft is enough on foot.
- Top up with a few inches of compost each spring; the soil keeps settling and breaking down.
Frequently asked questions
How much soil do I need for a 4×8 raised bed?
An 11 in tall 4 × 8 bed (two 2×6s) is 7′ 9″ × 3′ 9″ inside, which holds about 26.2 cubic feet once you allow for the posts. With 15% extra for settling, buy about 30.1 cubic feet: 1.11 cubic yards, or 21 bags of 1.5 cu ft raised-bed soil.
How much lumber do I need for a 4×8 raised bed?
For an 11 in tall bed, six 2×6 × 8 ft boards: four go on the long walls at full length, and two are each cut into two 3′ 9″ ends. You also need six 4×4 posts 22 in long (four corners and one in the middle of each long wall), cut from two 8 ft 4×4s, and 40 exterior screws.
Is bagged or bulk soil cheaper for a raised bed?
Bulk soil is much cheaper per yard, but the delivery fee dominates small orders. With $10 bags of 1.5 cu ft, $35 topsoil, $40 compost and a $75 delivery, one 11 in tall 4 × 4 bed costs $100 in bags (10 bags) against $112.50 in bulk. One 4 × 8 bed already costs $130 in bulk against $210 in bags.
How much water does a raised bed need?
About 1 in of water a week in summer, which is 0.62 gallons per square foot. A 4 × 8 bed has about 28.6 sq ft of growing area inside the boards, so it needs about 18 gallons a week when it doesn’t rain, and more in hot weather.
Is pressure-treated wood safe for a vegetable bed?
Lumber treated with CCA, which contains arsenic, is no longer sold for home use; today’s treatments (ACQ and copper azole) are copper-based, and the American Wood Protection Association rates ground-contact (UC4A) lumber for garden use. If you’d rather avoid treated wood, cedar and redwood resist rot on their own but cost more; untreated pine is cheapest but rots soonest.
How deep should a raised bed be?
Most vegetables need 6–12 in of rooting depth, and deeper is better. On a patio or other hard surface, University of Maryland Extension suggests at least 8 in for greens, beans and cucumbers and 12–24 in for tomatoes, peppers and squash.