Volume is easy; weight is where the money is
Working out how much soil covers an area is straightforward geometry: multiply the area by the depth. The only trick is that landscape work mixes units — area in square feet, depth in inches, material in cubic yards — so the arithmetic runs through a constant. Divide inches by 12 to get feet, then divide cubic feet by 27 to get cubic yards, and the two divisions collapse into a single division by 324.
The part that costs people money is the conversion from volume to weight. Landscape yards typically sell soil and mulch by the cubic yard; soil and gravel pits with a truck scale sell by the ton. To compare two quotes, or to know whether the truck arriving with "fifteen tons" carries enough, you need the material's bulk density. A cubic yard is 27 cubic feet, so a soil at 80 lb per cubic foot weighs 80 × 27 = 2,160 lb per yard, which is 1.08 tons. Change that density to 90 lb per cubic foot and the same yard weighs 1.215 tons — 12.5% more weight for exactly the same volume of soil on the ground.
Moisture is the single largest reason two loads of nominally identical topsoil weigh differently. Water fills pore space without adding any soil, so a screened topsoil dug after a wet week can be markedly heavier per cubic yard than the same product in August without covering any more ground. That is why buying by volume is more predictable for a coverage job and buying by weight is more predictable for the seller.
Each number, and where to get it
Area. Measure it rather than pacing it. For irregular shapes, break the space into rectangles, triangles and circles and add them; a triangle is half its base times its height, and a circle is π times the radius squared. Beds against a house wall are often several feet narrower than they look on a plan.
Depth. This is the finished depth over the prepared subgrade, and it is a design decision rather than a measurement. Two to three inches is a dressing over existing soil; four to six inches is a working topsoil layer for a new lawn; a raised bed or a planting hole is far deeper. Volume is directly proportional to depth, so an inch either way on a 1,000 ft² area is 3.09 cubic yards — a quarter of a typical delivery.
Bulk density. Bulk density is the dry weight of soil per unit of total volume, including the pore space, and USDA NRCS soil survey work reports it in grams per cubic centimetre. Mineral soils commonly fall between about 1.0 and 1.6 g/cm³ in place, with the lower end in well-structured loams high in organic matter and the upper end in compacted or sandy material. Screened topsoil that has been dug, handled and screened sits toward the lower half of that range because the handling loosens it, and then moisture adds weight back. The default of 80 lb/ft³ used here is 80 ÷ 62.428 = 1.28 g/cm³, comfortably inside the mineral-soil range. Your supplier's own figure beats any table.
Settlement allowance. Loose material placed and lightly firmed occupies less volume than it did in the truck, and some is always lost in handling and on the tyres. Ten percent is a common working allowance for a soil dressing; a deep fill that will be compacted in lifts needs considerably more. Running out one yard short is far more expensive than ordering one yard too many.
Worked example: 4 inches of topsoil over a 40 by 25 ft lawn area
You are dressing a new lawn area 40 ft by 25 ft to a finished depth of 4 inches. The supplier quotes screened topsoil at $32 a cubic yard delivered and tells you it runs about 80 lb per cubic foot. You want a 10% allowance, and the delivery truck carries 15 tons.
- Area. 40 × 25 = 1,000 ft².
- Volume before allowance. 1,000 × 4 ÷ 324 = 12.346 cubic yards.
- With the allowance. 12.346 × 1.10 = 13.580 cubic yards. Round up to 14 when you place the order.
- In cubic feet. 13.580 × 27 = 366.7 ft³.
- Weight. 366.7 × 80 = 29,333 lb, which is 29,333 ÷ 2,000 = 14.67 tons.
- Density per yard. 80 × 27 ÷ 2,000 = 1.08 tons per cubic yard, which is the number to quote when comparing a per-ton price.
- Truck loads. 14.67 ÷ 15 = 0.98, so one load — but only just, and a wetter soil at 90 lb/ft³ would be 16.5 tons and need two.
- Cost. 13.580 × $32 = $434.57 before delivery charges and tax.
Compare a competing quote of $30 a ton. At 1.08 tons per yard, $30 a ton is $30 × 1.08 = $32.40 a cubic yard, so it is marginally the more expensive material despite the lower headline number. Making that comparison requires the density, which is why it is worth asking for.
Reading the result and placing the order
Round up to the way the material is actually sold. Bulk soil goes out in whole cubic yards or whole truck loads, and a supplier will not deliver 13.58 yards. Order 14 and use the extra in low spots, which is exactly what the settlement allowance is for. Bagged product is sold in cubic feet: one cubic yard is 27 cubic feet, so a 13.58 yard job is 367 cubic feet, or about 184 bags at two cubic feet each — which is the calculation that usually decides people to buy in bulk.
Check the truck-load count against your site before the first delivery. A tandem or tri-axle dump body is limited by legal axle weight, not by how much soil fits in the box, so a 15-ton payload of soil at 1.08 tons per yard is about 13.9 cubic yards. If the number of loads comes out just above a whole number, decide whether trimming the depth by a quarter inch or reducing the allowance is worth saving a delivery fee.
Finally, remember that the depth you specify is the depth after firming, not the depth in the truck. If you spread to exactly four inches loose and then roll it, you will finish shallower than four inches. Spread proud, firm, and check with a probe or a spade cut in several places before you call the job done.
Soil required per 1,000 square feet
| Depth | Cubic yards | Cubic feet | Tons at 80 lb/ft³ |
|---|---|---|---|
| 1 in | 3.09 | 83.3 | 3.33 |
| 2 in | 6.17 | 166.7 | 6.67 |
| 3 in | 9.26 | 250.0 | 10.00 |
| 4 in | 12.35 | 333.3 | 13.33 |
| 6 in | 18.52 | 500.0 | 20.00 |
| 8 in | 24.69 | 666.7 | 26.67 |
| 12 in | 37.04 | 1,000.0 | 40.00 |
Multiply any row by your own area in thousands of square feet. A 2,500 ft² area at 4 inches is 2.5 × 12.35 = 30.9 cubic yards.
Bulk density in the three units you will be quoted
| g/cm³ | lb/ft³ | lb per cubic yard | tons per cubic yard |
|---|---|---|---|
| 1.0 | 62.43 | 1,686 | 0.843 |
| 1.1 | 68.67 | 1,854 | 0.927 |
| 1.2 | 74.91 | 2,023 | 1.011 |
| 1.3 | 81.16 | 2,191 | 1.096 |
| 1.4 | 87.40 | 2,360 | 1.180 |
| 1.5 | 93.64 | 2,528 | 1.264 |
USDA NRCS soil survey data reports bulk density in g/cm³, and mineral soils generally fall inside this range. Delivered, screened material also carries moisture, which raises the weight without changing the coverage.
Mistakes that leave you short or over-ordered
- Forgetting the settlement allowance. Loose soil placed and firmed occupies less space than it did in the truck, and a second small delivery costs far more per yard than the first.
- Assuming a cubic yard weighs a ton. It rarely does. At 80 lb/ft³ a yard is 1.08 tons; at 100 lb/ft³ it is 1.35 tons. Always get the density before comparing a per-yard price with a per-ton price.
- Mixing up depth units. The 324 constant expects inches. Entering 0.33 for four inches gives a hundredth of the material you need.
- Buying topsoil for a structural fill. Topsoil is graded for growing, not for supporting anything. Deep fill under a slab or a path is a different material, placed and compacted in lifts.
- Ignoring the subgrade. Soil placed on compacted, unbroken subsoil drains badly whatever its quality. Loosen the base before you spread.
- Measuring an irregular area as a rectangle. Curved beds and tapered strips are usually smaller than their bounding rectangle. Break the shape up and add the pieces.
Related materials and where the same arithmetic applies
Every bulk landscape material uses the same volume calculation and differs only in density. Mulch is much lighter than soil, so a per-yard price is nearly always the right basis for it; the mulch cubic yards calculator handles the depth conventions for bark and wood chip. Sod is sold by area rather than volume, and the sod square footage calculator deals with roll sizes and waste on curved edges. Sand, gravel and stone are heavier than topsoil and are almost always sold by the ton.
Once the soil is down, the follow-on decisions are fertility and seeding. Test before you amend rather than after: the soil test conversion calculator turns a laboratory report into pounds per acre, the lawn fertilizer rate calculator converts a nitrogen target into bag weight, and the grass seed rate calculator sizes the seed order for the same area you just measured here.
For very large jobs, note that the acre option in the area field lets you scale straight to field work. One inch of material over an acre is 134.4 cubic yards, which is a useful figure to carry: compost, manure and soil amendments applied at field scale are usually specified in tons per acre, and this calculator converts between the two directly once you know the density.