Topsoil is the cheapest thing in a garden project until you get the quantity wrong. A short delivery means a second delivery fee, and a long one leaves a mound on the driveway. The calculator turns your measurements into cubic yards (what a landscape yard sells), cubic feet (what bags are labelled in) and an approximate weight.
How to measure for topsoil
Work out the footprint first. For a lawn or a bed, measure length and width in feet and multiply. For a raised bed, use the inside dimensions of the frame, because the wood does not hold any soil.
Depth is the number people guess at, so measure it. Push a ruler or a screwdriver into the existing soil beside the area to see how much you need to build up. For a bed you are filling from scratch, the depth is the height of the frame less an inch or two, so the top does not sit flush with the rim.
The formula
Area in square feet times depth in inches, divided by 324, gives cubic yards. If you prefer feet, divide depth by 12 first and then divide the volume by 27. A quick check: 100 square feet at 4 inches is about 1.2 cubic yards.
For weight, multiply cubic yards by the density. Plain topsoil at a supplier is usually quoted at 2,000 to 2,500 lb per cubic yard, rising as it gets wetter. Blended raised-bed mixes with compost run lighter; one supplier states 1,500 lb per yard.
Worked example: two raised beds
Two raised beds, each 4 ft by 10 ft inside, filled to 10 inches.
- Area of one bed: 4 x 10 = 40 sq ft. Two beds: 80 sq ft.
- Volume: 80 x 10 / 324 = 2.47 cubic yards (the same as 66.7 cubic feet).
- Settling and spillage buffer of 10 percent: 2.47 x 1.1 = 2.72 cubic yards. Order 3 yards, or 2.5 if your yard sells in halves and you can top up.
- Weight: 2.72 yards of plain topsoil is roughly 5,400 to 6,800 lb. The same volume of a compost blend at 1,500 lb per yard is about 4,100 lb.
- In 2 cubic foot bags: 66.7 / 2 = 34 bags with no buffer, 37 with it.
Metric: two beds of 1.22 m by 3.05 m, 25 cm deep, which is about 1.9 cubic metres before the buffer.
Choosing a depth
Extension services and suppliers agree on the broad ranges:
- Raised beds: at least 8 inches for leafy greens, beans and cucumbers sitting on a hard surface, and 12 to 24 inches for tomatoes, peppers and squash (University of Maryland Extension). Beds set over loosened native soil can be shallower.
- New lawn or low spots: about 4 inches of topsoil, worked into the top few inches of what is underneath so there is no hard layer between the two. Tilling depth in the university lawn guides is 4 to 6 inches.
- Over sown grass seed: a quarter to half an inch is plenty.
- Established lawn: don't smother it. Extension advice for existing turf is a quarter to half an inch of fine material per pass.
What kind of soil are you buying?
Topsoil is the upper layer of natural ground, screened to remove stones. Quality varies with where it was dug. It is heavy, often heavy with clay or silt, and best for levelling, building up lawns and filling beds that will get compost mixed in.
Raised-bed or garden mix is a blend of topsoil and compost, sometimes with sand or bark. Maryland Extension suggests compost and topsoil blended at 1:2 or 1:1, or compost and a soilless mix at 1:1 for deep beds sitting on hard surfaces. It costs more per yard and weighs less.
Compost is not soil. It feeds and loosens, and it is normally mixed in rather than used neat. Oregon State suggests working a 3 to 4 inch layer into the top 8 to 12 inches for a new garden bed.
Fill dirt is whatever is cheapest to dig. It can hold rocks and subsoil, so it is not for planting.
Bags versus bulk
One yard is 13.5 bags of 2 cubic feet. A bed that takes 20 bags is a bulk order in disguise. Look at the guide on bags versus bulk to find where the price flips on your local quotes.
Common mistakes
- Using the outside size of the frame. Measure inside, or you over-order by the wall thickness times the perimeter.
- Filling to the rim. Soil settles after the first few waterings. Leave an inch or two, or order the buffer and top up later.
- Applying thick layers over grass. Several inches of soil over an existing lawn can kill it.
- Buying "topsoil" for a vegetable bed without asking what is in it. Ask about the compost fraction and whether it was screened.
- Ignoring the weight. One yard of moist topsoil can be at or past the half-ton payload of a pickup, so plan on delivery or two trips.
Values this calculator uses
Weights are loose, dry, typical figures in US tons (2,000 lb). Your supplier's numbers win if they differ.
| Item | Value | Source |
|---|---|---|
| Topsoil | 1.05 tons / cu yd (range 1 to 1.25) | earthstonerock.com, rosevillerocksupply.com, rosevillerocksupply.com; confidence: medium |
| Raised bed / planting mix | 0.75 tons / cu yd (range 0.75 to 0.75) | skynursery.com; confidence: low |
| Compost | 0.65 tons / cu yd (range 0.5 to 0.7) | skynursery.com, blog.harborsoils.com, rosevillerocksupply.com; confidence: low |
| 0.75 cu ft bag | 0.75 cu ft | sakrete.com, skynursery.com, travis-tx.tamu.edu |
| 1 cu ft bag | 1 cu ft | sakrete.com, skynursery.com, travis-tx.tamu.edu |
| 1.25 cu ft bag | 1.25 cu ft | sakrete.com, skynursery.com, travis-tx.tamu.edu |
| 1.5 cu ft bag | 1.5 cu ft | sakrete.com, skynursery.com, travis-tx.tamu.edu |
| 2 cu ft bag | 2 cu ft | sakrete.com, skynursery.com, travis-tx.tamu.edu |
Sources
- blog.harborsoils.com: cubic yard calculator landscape materials
- extension.umd.edu: soil fill raised beds
- extension.umd.edu: starting new lawn
- extension.oregonstate.edu: fs 270 raised bed gardening
- gardeningsolutions.ifas.ufl.edu: building raised beds
- skynursery.com: bulk calculator
- earthstonerock.com: cubic yards vs tons
- rosevillerocksupply.com: calculator
- travis-tx.tamu.edu: how much compost soil or mulch
- lancaster.unl.edu: uses compost landscape
- extension.oregonstate.edu: em 9308 how use compost gardens landscapes