Raised Bed Soil Quick Reference: Volumes and Fill Order

How much soil does a raised bed hold?

Multiply the inside length, inside width, and fill height, all in feet. A 4 × 8 ft bed filled 12 inches deep holds 4 × 8 × 1 = 32 cubic feet. That's about 1.2 cubic yards — more than 20 bags of 1.5 cu ft. Two or three beds quickly add up to a bulk delivery.

Common sizes at a glance

• 4 × 4 ft, 12 in deep: 16 cu ft (about 0.6 cu yd)
• 4 × 8 ft, 10 in deep: about 26.7 cu ft (about 1 cu yd)
• 4 × 8 ft, 12 in deep: 32 cu ft (about 1.2 cu yd)
• 3 × 6 ft, 18 in deep: 27 cu ft (1 cu yd)

What to fill it with

Most raised beds do well with a blend of good topsoil and compost. A common starting point is roughly 60% topsoil and 40% compost, adjusted for what you can source locally. Bagged raised-bed or garden mixes are a convenient option for one or two beds. Avoid filling beds with pure compost or straight native clay.

Saving soil in deep beds

Plant roots mostly use the top 12–18 inches. In beds taller than that, some gardeners fill the bottom with untreated logs, branches, leaves, or straw, then add soil on top. That organic material breaks down over time, so expect extra settling and plan to top up. If you use this method, enter only the soil layer's height in the calculator.

Fill in stages

1. Lay cardboard on grass at the bottom if you want to smother weeds
2. Add filler material (optional) for very deep beds
3. Add your soil blend in layers, watering each to help it settle
4. Top off to an inch or two below the rim
5. Expect to add a few inches more after the first season