Raised Garden Bed Soil

Turning Bed Dimensions Into Cubic Yards and Bags

Filling a raised bed just needs length × width × fill depth to find a volume. Enter your bed’s dimensions and this calculator converts that volume into cubic yards, cubic feet, and a standard-bag count.

The Formula

$$\vC{\text{Volume}} = \vA{\text{Length}} \times \vA{\text{Width}} \times \vB{\text{Depth}}$$

Source: standard volume geometry, converted to cubic yards (27 cubic feet each) for ordering, and to a 1.5 cubic foot bag count — a widely-sold bagged garden-soil size.

Worked Example

A 4ft × 2ft bed filled 1ft deep:

1. Volume: $\vA{4} \times \vA{2} \times \vB{1} = \vC{8}$ cu ft
2. Cubic yards: $\vC{8} \div 27 \approx 0.3$ cu yd
3. Bags (1.5 cu ft each): $\lceil 8 \div 1.5 \rceil = 6$

Key Factors to Consider

• Bagged soil settles noticeably after watering, so filling a bed exactly to the top on day one often isn’t enough. Loose, freshly-poured soil compacts once watered in, sometimes settling by an inch or more — many gardeners deliberately overfill slightly, or plan to top off the bed after the first watering, to end up at the intended fill depth.
• A raised bed doesn’t need to be 100% purchased garden soil — many gardeners blend it with compost or their own native soil to save cost. A common approach mixes bagged garden soil or a soil-compost blend with existing native soil (especially for a deeper bed), which can meaningfully reduce the total amount of purchased material needed compared to filling entirely with bagged product.
• Buying soil in bulk (by the cubic yard) is often cheaper per unit volume than buying the equivalent volume in bags, for a larger bed. Once total volume needed reaches roughly a cubic yard or more, checking a local garden center or landscape supplier’s bulk soil pricing against the bagged-count cost here is worth doing before committing to one or the other.
• Deeper isn’t always better — fill depth should match what’s actually being grown. Shallow- rooted crops (like lettuce or herbs) need less depth than deep-rooted ones (like tomatoes or root vegetables) — entering a depth that matches the specific plants planned for the bed avoids both under-filling and over-buying soil.

Common Mistakes

• Measuring the bed’s outer dimensions instead of the inner fillable space. The lumber or blocks forming a raised bed’s walls take up some of its footprint — measuring inside the finished walls gives a more accurate volume than measuring the bed’s outer frame.
• Not accounting for settling after the first watering. As noted above, freshly-poured soil compacts once watered in — filling exactly to the target depth on day one often leaves the bed looking underfilled a week later.
• Filling the whole bed with 100% purchased bagged soil when a blend would work just as well. For a deeper bed especially, blending in compost or existing native soil can meaningfully cut cost without hurting plant performance.

Useful to Know

• Want to check how far a bag of mulch will go on top of the soil? Mulch Calculator estimates mulch coverage from area and depth.
• Curious how much your own compost adds to the mix? Compost Volume Calculator estimates finished compost volume from what goes into the pile.
• Planning what to grow and how far apart to space it? Plant Spacing Calculator calculates how many plants fit a given bed area.