How Much Soil for a Raised Bed
To fill a raised bed, multiply its length by width by depth (all in feet) for cubic feet, then divide by 27 for cubic yards. A 4 by 8 foot bed 12 inches deep needs about 32 cubic feet, or roughly 1.2 cubic yards. A common fill is about 60 percent topsoil, 30 percent compost, and 10 percent aeration material.
How much soil
Measure the inside length, width, and depth of the box in feet. A 4 by 8 ft bed filled 12 inches deep is 4 x 8 x 1 = 32 cubic feet, or about 1.2 cubic yards. Half-fill depth halves the amount.
Soil settles, so fill to the top and expect to top up a little after the first watering and season.
A simple soil mix
A reliable raised-bed mix is roughly 60 percent topsoil or garden soil, 30 percent compost, and 10 percent an aeration material like coarse sand or perlite. The compost feeds plants while the topsoil gives body.
Use the topsoil and compost calculators for each part of the mix, then combine to your ratio.
FAQ
How much soil for a 4x8 raised bed?
About 32 cubic feet, or roughly 1.2 cubic yards, for a 12 inch deep bed. A 6 inch deep bed needs about half that.
What soil should I use in a raised bed?
A mix of about 60 percent topsoil or garden soil, 30 percent compost, and 10 percent aeration material such as coarse sand or perlite.
Can I use plain topsoil in a raised bed?
Topsoil works as the base, but mix in compost (about a third) so the bed drains well and feeds plants. Pure topsoil alone can compact.