How much soil for a raised bed: a filling guide
Measure a raised bed, work out cubic feet, choose bagged or bulk soil, and mix the right blend so plants get depth, drainage and nutrients.
Measuring the bed the right way
Accurate soil estimates start with the inside dimensions of the frame, not the outside of the boards. Measure the clear space between the inner faces of the timber for length and width, then decide how deep you want to fill. Depth is entered in inches here because bag labels and planting guides talk in inches, while length and width are in feet to match lumber. If a bed has stepped or sloped sides, take the average width so the volume is neither over nor under estimated.
Turning dimensions into a soil order
The volume of a rectangular bed is length times width times depth, with the depth converted from inches to feet by dividing by twelve. A 4 by 8 foot bed filled 12 inches deep works out to 32 cubic feet. Multiply by the number of matching beds to get a total. When that total climbs past roughly 15 to 20 cubic feet, bulk soil sold by the cubic yard is usually cheaper than bags, which is why the tool shows cubic yards alongside cubic feet.
Bags or bulk delivery
Bagged soil is convenient for one or two beds and easy to carry through a gate or up steps, but the per-cubic-foot price is higher. A single cubic yard equals 27 cubic feet, or roughly eighteen 1.5 cubic foot bags, so large projects add up fast in bags. Bulk delivery drops a pile on the driveway that you barrow to the beds, trading a lower price for more labor. The bag count and cubic yard figure let you compare both routes before you buy.
Building a mix that lasts
A raised bed is only as good as what fills it, so aim for a blend that drains yet holds moisture. A balanced starting point is one third quality compost for nutrients, one third topsoil or garden soil for body, and one third an aerating material such as perlite or coarse sand. Top up with an inch of fresh compost each season because organic matter breaks down and the level drops. Leaving headroom below the rim keeps water and mulch inside the bed rather than washing over the edge.