Topsoil calculator: yards, tons and bags

How to use the calculator

Type the length and width, or the area, and how deep the new soil goes. Pick the job and the calculator picks the soil and a depth; change either one. You get the yards to order with settling added, the weight, the bags and the pickup loads. The other tabs size a lawn-leveling mix, figure compost and show which soil goes where.

How it’s figured

Worked example. A new lawn of 400 sq ft at 4 inches: 400 × 4 ÷ 12 = 133.3 cubic feet, ÷ 27 = 4.94 cubic yards. Add 10 percent for settling and order 5.4 yards. At 1.15 tons a yard that is about 6.2 tons dry, or about 8.1 tons after a soaking rain. That’s 147 one-cubic-foot bags, which is why a job this size goes in bulk.

Metric. The Imperial | Metric switch at the top works in meters, centimeters, square meters, cubic meters, kilograms and metric tonnes; it opens in your region’s system and remembers your choice. The math is the same: 1 inch is exactly 2.54 cm, 1 foot exactly 0.3048 m, a cubic yard 0.764555 m³, and a US ton (2,000 lb) 0.907 metric tonnes. Bags stay as sold: a 1 cubic foot bag is about 28 liters.

Screened topsoil, garden mix or fill dirt?

Fill dirt is subsoil with little organic matter. It packs hard and stays put: holes, low ground, raising a grade, sloping away from the house. Spread it in layers of 4 to 6 inches and tamp each one. Grass grows poorly in it, so cap it with topsoil.

Screened topsoil has been run through a screen to take out stones, roots and clods. It’s what goes under a new lawn (4 to 6 inches), into low spots and into the leveling mix. Unscreened topsoil is cheaper and fine for rough grading, but the stones show through a thin layer.

Garden mix, also sold as blended or organic soil, is screened topsoil mixed with compost. It goes in vegetable gardens, raised beds and new flower beds. Keep it out from under lawns and patios: the compost breaks down and the ground sinks.

Lawn leveling: the 50/50 mix

The usual mix for leveling a lawn is half screened topsoil and half sand. The sand keeps it from crusting; the topsoil holds water. Clemson’s Home & Garden Information Center says to put down no more than half an inch at a time. Rake it in until the blades show and let the grass grow through before the next pass, about three to four weeks in the growing season.

A low spot is shaped like a shallow dish, and a dish holds about half of what a flat-bottomed hole the same depth would. The calculator uses that unless you pick a flat bottom. Deeper than about two inches, cut the sod, fill under it with screened topsoil, tamp it, and lay the sod back.

Other mixes people use: sand only, which works on sandy soils but can leave a layer on clay that water and roots don’t cross well (University of Florida Extension warns about this); 40 percent sand, 40 percent topsoil and 20 percent compost; and compost only, which is for a thin top-dress, not for filling. Whatever you choose, match it to the soil you have.

Compost: how much and where

Compost feeds soil and loosens it; it doesn’t build height. Oregon State University Extension suggests a quarter inch to an inch a year on existing beds, and three to four inches worked into the top six to eight inches when you start a new bed. On a lawn, a quarter inch right after core aerating falls into the holes and is gone in a week; that’s about three-quarters of a yard per 1,000 sq ft. For a raised bed with garden soil, the University of Maryland Extension aims for 25 to 50 percent organic matter by volume; the calculator starts at 30 percent compost and works out the topsoil for the rest. More is not better: too much compost at once can stunt plants.

Moving it: by hand or with a machine

Topsoil is lighter than stone but still heavy: the 5.4 yards in the example weigh about 12,500 pounds dry. A 6 cubic foot wheelbarrow holds about 3 cubic feet of it at a sensible 250 pounds a load, so that’s about 50 trips and 1,000 shovelfuls at the 11 to 15 pounds a scoop the Canadian Centre for Occupational Health and Safety suggests. Shoveling, walking 50 feet and raking come to about 9 hours for one person. A skid steer does it in under 2 hours, counting about an hour to pick it up, unload it and learn the controls, and you lift nothing. On a small pile that hour can make the barrow quicker, unless the machine is already there for the dig. A mini skid steer or a stand-on loader fits through a 36 to 42 inch gate, and rental stores carry them; a power wheelbarrow saves the walking, not the shoveling. Type your rental quote to see what each hour saved costs. The hours are estimates, the same ones the gravel calculator uses.

Weights, wet and dry, and bags

Screened topsoil weighs about 1.15 tons a cubic yard when it’s reasonably dry and around 1.5 tons when wet. Compost weighs about half as much. A half-ton pickup’s payload is often 1,500 lb or less, about one yard of wet topsoil; check the sticker in your door jamb. Bags are 0.75, 1, 1.5 or 2 cubic feet; one yard is 36, 27, 18 or 14 bags.

Settling: how much extra

Loose soil from the truck settles once it’s raked, rolled and watered. The calculator adds 10 percent for screened topsoil, 15 for garden mix and 20 for fill dirt and compost. Thin top-dressing gets none. If you plate-compact fill, plan on more.

Where the numbers come from

Depth per pass: Clemson University HGIC, “Topdressing a Home Lawn.” Sand-only layering: University of Florida IFAS Extension. Compost rates: Oregon State University Extension EM 9308. Raised-bed organic matter: University of Maryland Extension. Compost weight: the City of Columbus compost facility’s 1,000 lb a yard, with SARE’s measured samples lower. Topsoil weights: supplier and university figures from 1 to 1.15 tons dry and 1.3 to 1.7 tons wet. Grading away from the house: IRC R401.3, six inches of fall in the first ten feet; your building department decides which edition applies.

Tips and common mistakes

• Slope fill and topsoil away from the house, never toward it, and keep soil below the siding.
• Don’t bury a lawn under more than half an inch at once; it smothers.
• Ask the yard if it’s screened, and look at a scoop before the truck comes.
• A skid steer on a lawn tears the turf at the turns: lay plywood, or rent a tracked machine.

Questions

Read the guide: Topsoil to level a lawn →

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