Loam Calculator

This calculator gives an estimate for ordering, not a survey-grade figure. Weight uses published loam densities, and real soil shifts with moisture, organic content, and compaction. Treat the number as a close guide for buying, and add a cushion for settling.

How to use this calculator

1. Pick the shape of the area you are covering: rectangle or square, circle, triangle, or enter a known square footage directly.
2. Enter the matching measurements in feet, then set how deep you want the loam in inches.
3. Choose the loam condition: dry, moist (typical topsoil), or wet, which sets the density used for the weight estimate.
4. Pick a bag size if you are buying bagged loam, or choose bulk only to hide the bag count.
5. Read the volume in cubic yards and cubic feet, the weight in tons and pounds, the bags needed, and how much area one cubic yard covers at your depth.
6. Change any field to compare depths, shapes, or moisture conditions; the result updates as you type.

How it works

This calculator turns a few measurements into everything you need to order loam or topsoil. It starts with your area in square feet. Pick a rectangle and enter length and width, pick a circle and enter the diameter, pick a triangle and enter the base and perpendicular height, or type the square footage if you already know it.

Next it converts your depth from inches to feet and multiplies it by the area to get the volume in cubic feet. Because soil is sold by the cubic yard, it then divides by 27, since a cubic yard is a 3-by-3-by-3-foot cube that holds exactly 27 cubic feet.

To estimate weight, it multiplies the volume by the bulk density of loam. Bulk density is the weight of the soil per unit of volume, and loam is not a fixed weight. A published materials table lists dry loam at about 78 pounds per cubic foot, moist loam or typical screened topsoil at about 90, and wet loam at about 100 (SI Metric materials density). The tool lets you pick the condition and shows which number it used. Multiply that out for pounds, then divide by 2,000 for US tons. Those constants sit inside the 1.0 to 1.6 grams per cubic centimeter range that published references give for mineral soil (Bulk density, Wikipedia), and independent extension and government sources place loam around the same band (SDSU Extension).

If you are buying bags rather than bulk, the tool divides your volume by the bag size you pick and rounds up to whole bags. Finally it tells you how many square feet a single cubic yard covers at your chosen depth, which helps when you have a fixed delivery and want to know how thick you can spread it.

Everything is plain geometry and documented density constants, so the same inputs always give the same answer. Add roughly 10 percent extra for settling, uneven ground, and spillage.

Examples

If you top a 20 ft by 10 ft garden bed with 4 inches of moist loam, the tool returns 2.47 cubic yards. The area is 20 by 10, or 200 square feet. The volume is 200 times 4/12, which is 66.67 cubic feet, then divided by 27 for 2.47 cubic yards. At 90 pounds per cubic foot, that weighs 6,000 pounds, or 3.00 tons. In 0.75 cubic foot bags, that is 89 bags, and one cubic yard covers 81 square feet at 4 inches.

If you fill a round bed 12 feet across with 3 inches of dry loam and order bulk, the tool returns 1.05 cubic yards. The circle area is pi times 6 squared, or 113.1 square feet. The volume is 113.1 times 3/12, which is 28.27 cubic feet, or 1.05 cubic yards. At 78 pounds per cubic foot, that weighs 2,205 pounds, or 1.10 tons. With bulk chosen, no bag count shows, and one cubic yard covers 108 square feet at 3 inches.

If you already know a 500 square foot lawn area and want 6 inches of moist loam in 1 cubic foot bags, the tool returns 9.26 cubic yards. The volume is 500 times 6/12, which is 250 cubic feet, or 9.26 cubic yards. At 90 pounds per cubic foot, that weighs 22,500 pounds, or 11.25 tons, in 250 bags. At 6 inches, one cubic yard covers only 54 square feet, so a 6 inch lawn build-up is a big order.

What the data says

Most people land here with two worries at once: how many yards do I actually order, and will the pile dumped in the driveway look short. The math below settles the first, and a 10 percent cushion settles the second.

The biggest surprise is how much depth changes the order, and the two depths in play are easy to confuse. Starting a new lawn means working amendments into the top 4 to 6 inches of soil, which is the prep and tilling depth, then spreading only about a quarter to a half inch of topsoil or finished compost over the sown seed, which is the thin layer you actually buy and spread (University of Maryland Extension). University extension turf specialists put a number on that topsoil layer:

“Use only about ¼ to ½ inch of topsoil or good-quality finished compost on top of sown seeds.”

University of Maryland Extension, in Starting a New Lawn.

The deeper you spread a yard, the less ground it covers, which is the figure most buyers actually want before they commit to a depth. This table is the exact “coverage per cubic yard at this depth” number the calculator reports for any depth you enter, turning an abstract conversion into a buying decision:

Spread depth	Coverage of 1 cubic yard	Typical use case
1 in	324 sq ft	Light top-dressing an existing lawn
2 in	162 sq ft	Top-dressing and leveling low spots
3 in	108 sq ft	Overseed prep, thin new beds
4 in	81 sq ft	New lawn seeding base, garden beds
6 in	54 sq ft	Sod base, deeper bed build-up
12 in	27 sq ft	Raised bed or heavy fill

Weight is a range, not a single constant. A healthy loam sits around 1.4 grams per cubic centimeter, about 87 pounds per cubic foot, at ideal porosity, but it gets denser as it compacts and takes on moisture. That is why the same cubic yard of loam can weigh anywhere from roughly 1.05 to 1.35 US tons depending on its condition (USDA Natural Resources Conservation Service). The tool exposes a dry, moist, or wet input instead of hiding one weight.

A few mistakes come up again and again:

• People often mix up cubic feet and cubic yards by forgetting to divide by 27, or mix inches of depth with feet of area, which leads to ordering far more or far less than they need.
• People often treat tons and cubic yards as the same thing when one supplier quotes by weight and the next quotes by volume, so they cannot compare prices. A yard of loam is roughly 1 to 1.3 tons, and the exact figure depends on how wet it is.
• People often order exactly the calculated amount, then find the bed or lawn sits low after the soil settles and is watered in. A common reply from veterans is to always order about 10 percent extra.

What this tool does that others don’t

• It publishes the exact bulk-density constants it uses and lets you pick the moisture condition: dry at 78, moist at 90, or wet at 100 pounds per cubic foot (SI Metric materials density). Many supplier calculators bake in a single hidden density, so you cannot check the tonnage or adjust it for wet versus dry material.
• It returns cubic feet, cubic yards, tons, pounds, and a bag count from one entry. Tools that report cubic yards alone leave a homeowner buying bags, or a contractor ordering by weight, to do a second calculation by hand.
• It offers four area shapes: rectangle, circle, triangle, and a direct square-footage entry. Real beds are often round or triangular, while many calculators accept only a rectangle or a pre-computed square footage.
• It shows the tons math in the open, with the 1 cubic yard equals 27 cubic feet conversion explained and a worked example from area to cubic feet to cubic yards to tons, so you can verify every step.
• It reports coverage per cubic yard at your chosen depth, the number most people want when deciding how deep to spread a fixed delivery.

Frequently asked questions

How do I calculate how much loam I need?

Measure the area you want to cover in square feet, then decide how deep you want the loam in inches. Multiply the area by the depth in feet (depth in inches divided by 12) to get cubic feet, then divide by 27 to get cubic yards, which is how bulk loam is sold. This calculator does all of that for you and also gives the weight in tons and the number of bags.

How many tons is 1 yard of loam?

It depends on moisture. Using documented loam bulk densities, one cubic yard weighs about 1.05 US tons when dry (2,106 lb), about 1.22 tons when moist or as typical screened topsoil (2,430 lb), and about 1.35 tons when wet (2,700 lb). A common rule of thumb is roughly 1 to 1.3 tons per cubic yard. This tool lets you pick the condition so the weight matches what you are actually buying.

How many cubic feet are in a cubic yard of loam?

Exactly 27. A cubic yard is a cube three feet on each side, and 3 by 3 by 3 equals 27 cubic feet. This is a fixed unit conversion, not a property of the soil, so it is the same for loam, mulch, gravel, or anything else sold by the yard.

How many bags of loam equal a cubic yard?

It depends on the bag size. A cubic yard is 27 cubic feet, so it takes 36 of the common 0.75 cubic foot (40 lb) bags, 27 of the 1 cubic foot bags, or 18 of the 1.5 cubic foot bags to equal one cubic yard. Bags get expensive fast above a yard or two, which is why larger jobs are usually ordered in bulk.

How deep should loam be for a new lawn?

There are two depths, and they are easy to mix up. The 4 to 6 inches is the prep depth: you work amendments into the top 4 to 6 inches of soil before seeding. The topsoil you actually spread over the sown seed is only about a quarter to a half inch of loam or finished compost. For garden and raised beds, 6 to 12 inches is common. Enter your target depth and the tool shows how much that works out to.

How much area does a cubic yard of loam cover?

One cubic yard spreads over 324 square feet at 1 inch deep, 162 square feet at 2 inches, 108 square feet at 3 inches, and 81 square feet at 4 inches. The deeper you spread it, the less ground it covers. This calculator reports the coverage per cubic yard at whatever depth you enter.

Why does the tool ask whether the loam is dry, moist, or wet?

Soil weight comes from its bulk density, and that changes a lot with moisture. The same volume of loam can weigh anywhere from about 78 to 100 pounds per cubic foot depending on how wet it is. Picking the condition gives you a more honest tonnage. If you do not know, choose moist, which matches typical delivered topsoil.

Is loam the same as topsoil?

Not exactly. Topsoil is just the top layer of soil and can be any texture. Loam is a specific texture, roughly 40 percent sand, 40 percent silt, and 20 percent clay, prized for holding moisture and nutrients while still draining well. Good screened topsoil is often loamy, which is why the two are sold and calculated almost interchangeably. The volume and weight math is identical either way.

Sources

• SI Metric, Density of materials. The bulk-density constants for excavated earth and loam: dry 78, moist 90, and wet 100 pounds per cubic foot.
• Bulk Density is an Indicator of Soil Health, South Dakota State University Extension. University-extension confirmation that loam bulk density sits in the same band as the constants used here.
• Soil Bulk Density / Soil Health Guide, USDA Natural Resources Conservation Service. Government values placing ideal loam density near 1.40 grams per cubic centimeter, about 87 pounds per cubic foot.
• Bulk density, Wikipedia. Supporting reference: dry mineral-soil bulk density runs 1.0 to 1.6 grams per cubic centimeter, and weight equals bulk density times volume.
• Starting a New Lawn, University of Maryland Extension. Work amendments into the top 4 to 6 inches of soil, then spread only about a quarter to a half inch of topsoil or finished compost over the sown seed.
• Soil Health, USDA Natural Resources Conservation Service. Loam bulk density near 1.4 grams per cubic centimeter at ideal porosity, rising as soil compacts and takes on water.