The best soil mix for raised beds

Last reviewed 2026-06-06

Great raised-bed harvests start with the soil. Here is a forgiving mix that works — and how to fill deep beds without overspending.

A raised bed lives or dies by its soil. Bagged “raised bed mix” works but is pricey at volume, and plain topsoil alone compacts. A simple homemade blend grows better plants for less money.

A forgiving recipe

A reliable mix is roughly 60% quality topsoil, 30% compost and 10% aeration (perlite, coarse sand or fine bark). The topsoil gives body, the compost feeds the plants and holds moisture, and the aeration stops it compacting so roots can breathe.

Why not 100% compost?

Pure compost sounds rich but it shrinks dramatically, holds too much water, and can be too strong for seedlings. Blending it with topsoil gives a stable structure that lasts the season.

Filling deep beds cheaply

For a deep bed, you do not need premium mix all the way down. Fill the bottom third with cheaper bulk material — coarse compost, fallen leaves, small branches or untreated wood (a “hügelkultur” base) — and reserve the good mix for the top 8–12 inches where roots live.

Top up every year

Organic matter breaks down, so the level drops each season. Top up with an inch or two of compost annually to keep the bed fertile and full.

How much will you need?

The raised bed soil calculator turns your bed size, fill depth and number of beds into litres, bags and cubic feet — so you buy the right amount of mix in one go. For a bulk delivery of topsoil or compost, work out the cubic yards first.

Calculators for this

• Raised Bed Soil Calculator — Litres, bags or cubic feet of soil to fill raised beds.
• Mulch Calculator — Cubic yards or bags of mulch for your beds.