From Tape Measure to Shopping List: Building and Filling a 4 × 8 Raised Bed

The 4 × 8 foot raised bed is the standard for good reasons. Four feet is as wide as most people can reach across from both sides without stepping on the soil, and eight feet is a standard length of lumber, so the long sides need no cutting. This guide follows one bed all the way through, with every number worked out, so that you can copy it or adapt it.

Step 1: Choose the place

A vegetable bed wants:

• Sun. At least six hours of direct sun a day for most vegetables. Watch the spot through a day before you commit.
• Level ground, or close to it. A bed built on a slope has soil level with the rim at one end and a deep gap at the other.
• Water within reach. If the hose does not reach comfortably, the bed will not get watered.
• Access all around. Leave at least 2 feet on every side, and 3 feet if you want to get a wheelbarrow past.
• Distance from trees. Tree roots will find the good soil in a raised bed within a season or two.

Step 2: Decide the size and height

Width: 4 feet, or 3 feet if the bed will sit against a fence and can be reached from one side only.

Length: 8 feet. Longer beds work, but the sides bow outward under the weight of the soil unless you brace them in the middle.

Height. Two boards high, using 2 × 6 lumber, gives sides 11 inches tall, because a 2 × 6 is really 5½ inches wide. That is deep enough for nearly every vegetable, including carrots. One board high, 5½ inches, is enough over good existing soil. Three boards high, 16½ inches, is easier on the back and takes half as much soil again.

This walkthrough builds the two-board version.

Step 3: The lumber

Which wood? Cedar and redwood resist rot naturally and last ten years or more, at a price. Untreated pine or fir is cheap and lasts three to five years. Modern pressure-treated lumber no longer contains the arsenic compounds used before 2004, and many university extension services consider it acceptable for vegetable beds. Some gardeners still prefer to avoid it, or line the inside with heavy plastic. That choice is yours. Avoid old railroad ties and any reclaimed lumber of unknown history.

Step 4: The cuts, and the real inside size

Cut two of the 8 foot boards exactly in half, giving four end boards of 48 inches. Cut the 4 × 4 into four blocks of 11 inches.

Now the detail that most plans skip. The end boards cap the ends of the long boards.

• Inside length: 96 inches. The long boards run the full 8 feet between the end boards.
• Inside width: 48 inches minus the thickness of the two long boards, 1½ inches each. That is 45 inches, or 3 feet 9 inches.
• Inside area: 8 × 3.75 = 30 square feet, not 32.

Two square feet does not sound like much. It is 6% of the soil order, and it is why measuring the inside matters.

Step 5: Build the frame

1. Lay out one course on a flat surface: two long boards and two end boards, with a corner block standing inside each corner.
2. Screw through the boards into the corner blocks, three screws at each board end. Drill pilot holes first to avoid splitting.
3. Stack the second course on top and screw it to the same corner blocks.
4. Carry the frame to its place. It takes two people.

The whole frame takes about an hour with a drill and a saw.

Step 6: Prepare the ground

• Mark the outline and remove any sod inside it, or mow it as short as possible.
• Level the frame. Set it in place and check with a level along each side. Dig out the high side until it sits flat. Do not prop up the low side with soil, which settles.
• Lay cardboard over the ground inside the frame, overlapping the pieces by several inches, and soak it. It smothers grass and weeds and rots away within a season.
• Loosen the soil underneath with a fork before the cardboard goes down, if it is very compacted, so roots can go deeper than the bed.
• Where burrowing animals are a problem, staple galvanized hardware cloth across the bottom of the frame before setting it down.

Step 7: Calculate the soil

The bed is 11 inches tall inside. Leaving a 1 inch gap at the top gives 10 inches of soil.

Using a 60 / 30 / 10 mix, bought in 1.5 cubic foot bags:

Nineteen bags weigh well over 1,000 pounds in all. That is several car loads, or one or two loads for a pickup, depending on its payload.

The alternative is a bulk delivery of one cubic yard of blended raised bed mix. A yard is 27 cubic feet, which is almost exactly what this bed needs. For a single bed, compare the delivery fee against the cost of 19 bags. For two beds or more, bulk nearly always wins. Our guide to bagged versus bulk shows how to work out the break-even.

For more on choosing a recipe, see the guide to raised bed soil mixes.

Step 8: Fill it

1. Add the ingredients in layers, a few inches of each at a time, and mix them with a fork or a rake as you go.
2. Water each 4 inch layer. Dry compost and peat shed water until they are wetted through.
3. Fill to about an inch below the rim, mounding very slightly in the middle.
4. Water the whole bed thoroughly and leave it for two or three days.
5. Top up any hollows before planting.

Step 9: Plant and mulch

How many plants? At 30 square feet:

Most beds mix several crops, so use the plant spacing calculator for each block of the bed separately.

Mulch. An inch or two of straw or shredded leaves over the surface holds moisture and keeps soil from splashing onto leaves. One inch over 30 square feet is 2.5 cubic feet, a small fraction of a straw bale.

The complete shopping list

Or, in place of the 19 bags: one cubic yard of blended raised bed mix, delivered.

Adapting the numbers

The same method works for any size. Change one measurement and follow it through.

• A 4 × 4 bed has an inside area of about 4 × 3.75 = 15 square feet and takes half of everything: about 14 cubic feet of mix.
• A three-board bed, 16½ inches tall, holds 15½ inches of soil. That is 30 × 15.5 ÷ 12 = 39 cubic feet, or 43 with the settling allowance. Fill the bottom 5 inches with logs and branches and you are back to the two-board order.
• Several beds. Multiply by the number of beds. At three beds, you need about 3 cubic yards, and a bulk delivery is the only sensible way to buy it.

Put your own inside measurements into the raised bed soil calculator and it will produce the same breakdown for whatever you build.

Written and checked by Bertha
Last updated October 4, 2026 · How we work out our numbers