To fill a raised garden bed, calculate its volume, set the bed in its final spot, add a base layer if needed and then fill with a planting mix in stages, wetting and settling as you go. Fill is bulky, so work out the amount before you order. The steps and table below cover the job from measuring to topping up.
Calculate the Volume
Multiply length by width by the depth you want to fill. Work in the same units throughout, then convert to cubic feet, cubic yards or cubic meters to match how the supplier sells fill. Leave a small gap below the rim so water does not spill over.
| Bed size (L x W x D) | Volume |
|---|---|
| 4 ft x 4 ft x 1 ft | 16 cubic feet |
| 4 ft x 8 ft x 1 ft | 32 cubic feet |
| 3 ft x 6 ft x 1.5 ft | 27 cubic feet |
| 1.2 m x 2.4 m x 0.3 m | about 0.86 cubic meters |
One cubic yard equals 27 cubic feet, which helps when a supplier sells by the yard.
Prepare the Base
- Set the bed on level ground in its final position, because it cannot be moved once full.
- Clear large stones and loose debris from the area.
- If the ground below is grass, you can lay down flattened cardboard or a landscape fabric, following the maker’s directions.
- If the bed sits on a hard surface, check that drainage holes are clear.
Fill in Stages
- Add a bottom layer of coarse, natural material such as small branches or leaves if you want to use up yard waste and reduce the amount of purchased soil.
- Pour in the planting mix in layers of about 10 to 15 cm (4 to 6 in).
- Rake each layer flat and water it lightly so the material settles.
- Repeat until the mix is a couple of centimeters below the rim.
- Level the surface and water the whole bed slowly.
Settling and Topping Up
Soil sinks as it settles, so expect the level to drop after a few waterings. Keep a little extra mix on hand to top up. Read the label directions of any bagged product, and ask the supplier how they recommend mixing different materials. Wear gloves while shoveling, lift with your legs, and wash your hands with soap and water once the job is done.
FAQ
Should I use soil from my yard?
You can mix it in, but a purpose-made planting mix usually drains and handles better in beds. Blend ingredients as the supplier suggests.
How deep should the bed be filled?
Fill to near the rim. Shallow-rooted crops need less depth, while deeper roots appreciate more, so check your seed packets.
The Short Version
Measure, calculate volume, level the site and fill in stages, wetting each layer. Top up after the soil settles.