4-square 8-foot raised bed in 12 inches of depth requires around 1.19 cubic yards of soil. Around 16 bags of 2 cubic feet size. That beats the expectations of many folks.

If you double the length to 4-by-16, you reach 2.37 yards what can weigh around 2 400 pounds with dense garden ground mix. The weight of potting-mix is fairly light, between 400 and 700 pounds each yard, while compost arrives at almost 1 000. Always I plan 10% extra, because settling removes 5 to 15 percent of the volume after the first good soaking.

How Much Soil Do Raised Beds Need and What to Use

For every square foot in 12 inches depth you need around 0.037 cubic yards, the math is really hard. 5-by-10 bed? Only less than 1.9 yards.

Sandy loam soil can reach 2 800 pounds each yard, so know that is not a game.

The info below does not come from some calculator or converter. It is based on real use, reviews, forum talks and experiences from garden groups across the net.

Soil for raised beds must be light and well draining. One can make good mix mixing equal parts of topsoil, organic stuff as compost or peat with coarse sand. The main target is soil, that keeps moisture without allowing roots to sit in water too long, because plants really hate that.

Too wet soil can make plants rot.

Common way is use 50% topsoil and 50% organic stuff as compost or stable dressing. Even better mix is made up of 50% topsoil, 30% compost and 20% peat moss. Add around 10% perlite is useful, if the local soil is heavy clay.

Extra advised mix is 60% topsoil, 30% compost and 10% potting-soil, that is soilless mix with peat moss, perlite or vermiculite.

One detailed recipe uses 39% peat, 39% compost, 10% very coarse vermiculite, 10% perlite and a bit of dolomite lime and sulphur. Other versions combine five parts of topsoil, four parts of compost, two parts of peat moss and two parts of perlite.

Topsoil from the upper three to six inches of landscape soil is rich in nutrients and drains well. It works well for raised beds, if it was not treated with chemicals or insecticides. Before setting up raised beds on your chosen spot, remove any grass or lasting weeds from the area.

Breaking the surface of the ground also helps before adding soil. Over time, healthy soil in raised beds will improve the underground health below.

For more small beds, bagged organic raised bed mixes and potting-mixes work well. Mix in a bit of aged stable manure in the upper few inches to give extra nutrients. Additives with things as perlite, manure, bed, plaster and peat moss help loosen the soil, keep moisture, improve the texture, reduce diseases and add nutrients.

Fill beds with logs, fresh wood chips and compost up is another weigh. One calls this method Hügelkultur, and it is a cheap way to fill raised beds, especially if one has free logs and branches. Compost and topsoil commonly sell at landscape suppliers or websites for around 40 to 50 dollars each cubic yard.

4-by-8 foot bed in six inches depth needs eight bags of soil. The same bed in 12 inches depth needs around 16 bags. Soil sells in bags each cubic foot or each yard for big purchases.

Local soilsuppliers commonly offer already mixed mixes ready to use, what saves time and work.