Topsoil Calculator

How much topsoil do I need?

Topsoil has one convenient property: screened topsoil weighs close to 2,000 pounds per cubic yard, so a cubic yard is very nearly a ton. That makes mental checks easy, and it is why suppliers in a lot of regions quote the two interchangeably.

The math is the same as any bulk material. Area times depth gives cubic feet, divide by 27 for cubic yards. A cubic yard covers 324 square feet at one inch, 54 square feet at six inches, and 27 square feet at a full foot.

Soil settles, so order proud

Fresh soil is full of air. Once it is watered in and walked on, it drops. How much depends on the organic content: straight screened topsoil settles maybe 10 percent, a compost heavy garden mix can settle 20 to 25 percent in the first season.

For raised beds this matters more than anywhere else, because you notice the drop immediately. Fill a 12 inch box to the rim with compost blend and by midsummer you are looking at 9 or 10 inches. Either fill it proud and mounded, or plan on topping up in year two. For lawn repair, a little settling is fine and often desirable, since soil mounded above grade looks wrong until it drops in.

Topsoil, garden mix or fill dirt

These are three different products and they are not interchangeable, though they often sit in adjacent piles at the same yard.

• Screened topsoil is native soil run through a screen to pull out rocks and roots. It is the default for lawns and general grading. Quality varies enormously between suppliers, so ask what it was screened from.
• Garden mix or raised bed mix is topsoil cut with compost and sometimes bark fines or sand. Lighter, better drained and far better for growing than straight topsoil, which compacts into a brick in a raised box.
• Fill dirt is unscreened subsoil. It is for changing grade, filling holes and building up under something. Nothing grows in it. Use it for bulk volume and cap it with real topsoil.

For a raised vegetable bed, do not fill the whole thing with garden mix at $60 a yard. Fill the bottom half with cheaper fill or a topsoil and compost blend and reserve the good stuff for the top 8 to 12 inches, which is where the roots actually live.

Topsoil weight and your truck

A cubic yard of screened topsoil is about a ton dry. After a week of rain it can hit 2,700 pounds, which is a 35 percent swing. If your supplier weighs the truck rather than measuring volume, order after a dry spell and you get more soil for the same ticket.

One yard is the practical limit for a half ton pickup. Two yards is over two tons and will overload it. Delivery is usually the right answer for anything past a single yard.

Levelling a lawn

For filling low spots in an existing lawn, do it in stages rather than all at once. Grass will grow up through about half an inch of topsoil without trouble. Bury it under three inches and you kill it and have to reseed.

So for a dip that needs two inches of fill, apply half an inch, let the grass grow through and mow it twice, then repeat. It takes a season but you never lose the turf. For anything deeper than about two inches, it is faster to cut the sod out, fill underneath and lay it back.

Common questions

How much does a yard of topsoil weigh?

Roughly 2,000 pounds, or one ton, for screened topsoil at normal moisture. Wet topsoil can reach 2,500 to 2,700 pounds per yard. Compost heavy garden mixes are lighter at around 1,400 to 1,800 pounds.

How many bags of topsoil are in a cubic yard?

27 bags at 1 cubic foot each, 18 bags at 1.5 cubic feet, or 13.5 bags at 2 cubic feet. Bagged soil costs several times what bulk does, so bulk is worth it for anything past about half a yard.

How deep should topsoil be for a new lawn?

Four to six inches of good topsoil over prepared subgrade. Less than four and the lawn dries out fast and struggles in summer. If you are working over compacted builder subsoil, break that up before adding topsoil or you create a perched water table.

How much soil do I need for a raised bed?

Multiply length by width by depth in feet and divide by 27 for cubic yards. A 4 by 8 foot bed at 12 inches deep is 32 cubic feet, which is about 1.2 cubic yards. Fill it proud, compost heavy mixes settle 20 percent or more in the first season.

Is topsoil the same as fill dirt?

No. Topsoil is screened, biologically active and meant for growing. Fill dirt is unscreened subsoil used for changing grade and filling holes, and nothing grows well in it. Use fill for bulk volume and cap it with topsoil.

These figures are planning estimates. Bulk material weight shifts with moisture and screen size, and suppliers round differently, so confirm the final quantity with your yard before you order.