GUIDE深度 · Deep dive
How Much Soil for a Raised Garden Bed?
Raised bed soil volume = length times width times depth. Bagged soil is usually sold in cubic feet and bulk soil in cubic yards; calculate volume, then add about 10% for settling. Deep-root crops need a deeper bed.
Unify the units
Feet: length times width times depth in feet = cubic feet.
Cubic yards = cubic feet divided by 27.
Add up the labeled volume of bags; do not guess from weight.
Soil and drainage
Use a topsoil/compost mix, not only native dirt.
A drainage layer/coarse material reduces the actual soil volume.
Soil settles after watering; leave about 10% headroom.
FAQ
Is 12 inches deep enough?
Usually enough for greens/herbs; tomatoes/root crops often want 18–24 inches.
How many cubic feet are in a bag?
Commonly 1, 1.5 or 2 cubic feet; check the label.
Do I need gallons?
One cubic foot is about 7.48 gallons, for reference.