Measure the space you want to fill and choose the finished depth. We’ll show the volume in cubic feet and cubic yards, along with a bag count and a separate settling allowance.
Soil sold for levelling a lawn may not be the right mix for a vegetable bed. Confirm the material as well as the amount with your supplier.
How to use this calculator
- Measure the inside of the bed frame, not the outside — timber thickness counts.
- Set the fill depth a couple of inches below the frame top so watering does not wash soil over the edge.
- Calculate the total volume, then split it into your soil mix proportions.
- Order with the settling allowance if the beds are new; topping up later is normal either way.
How soil volume is calculated
Volume in cubic feet = length × width × (fill depth in inches ÷ 12) × number of beds. Cubic yards = cubic feet ÷ 27. The base bag count assumes 1.5 cubic feet per bag and rounds up. A separate result adds 15 percent to the base volume for comparison; that extra amount is not included in the base bag count and does not predict actual settling.
One 8 ft x 4 ft raised bed filled 12 inches deep holds 32 cubic feet of soil: 1.19 cubic yards in bulk, or 22 bags of 1.5 cu ft. With settling, plan on about 37 cubic feet across the first season.
A few things worth checking
- Measuring the outside of the frame and over-ordering by the full timber thickness on every side.
- Filling the whole bed with bagged compost alone — expensive, and often too rich and loose for roots compared with a topsoil-based mix.
- Ignoring delivery access: a cubic yard of wet topsoil weighs well over a ton, and barrowing it from the street is real work.
Your questions, answered
How much soil does an 8x4 raised bed take?
At a measured fill depth of 12 inches, an 8x4 ft rectangle holds 32 cubic feet: about 1.19 cubic yards or 22 bags of 1.5 cu ft, rounded up. This base quantity excludes the separately shown settling allowance.
Does the tool account for other fill layers?
No. It calculates the rectangular volume from the depth you enter. If only part of a bed needs the material you are ordering, measure that fill depth rather than using the full outside height of the frame.
Does this choose the right soil or compost?
No. It estimates volume; it does not select a growing medium or check suitability for your plants. Confirm the material and the volume supplied per bag or bulk unit before ordering.
How is the settling allowance calculated?
The tool shows a separate volume with 15 percent added to the base volume. That fixed comparison does not predict how much your actual material will settle. The displayed 1.5 cu ft bag count is based on the base volume, without that extra 15 percent.
A Simple Materials Checklist for Your Next DIY Project
Keep the measurements, materials and small forgotten bits on one page before you shop.