Topsoil vs Fill Dirt vs Garden Soil
Topsoil is the surface layer of the soil, the A horizon in Utah State Extension's words; fill dirt has no standard definition in the sources opened, and UC ANR uses "fill soil" for subsoil dug in cut-and-fill work.
Estimates for planning, not professional advice. Read the full notice.
Work it out for your own sizes
Work out the yards for your own spotExample to try: Length 10 ft, Width 10 ft, Depth 6 in
Topsoil and fill dirt: weight and yards to order
Weight per cubic yard of top soil and fill dirt from New Mexico EMNRD, and the loose cubic yards to order for the example area with and without an allowance for compaction
| Material, depth and source of the depth | Tons per cubic yard (New Mexico EMNRD; the source does not say loose or compacted) | Cubic yards to order, no allowance | Cubic yards to order, with an allowance for compaction |
|---|---|---|---|
| Topsoil, 4 in deep (Penn State's lower lawn depth) | 0.8 ton/yd³ | 1.23 yd³ | 1.76 yd³ |
| Topsoil, 6 in deep (Penn State's upper lawn depth) | 0.8 ton/yd³ | 1.85 yd³ | 2.65 yd³ |
| Fill dirt, 6 in deep (the example low spot) | 0.8 ton/yd³ | 1.85 yd³ | 2.65 yd³ |
Estimate for planning, from what you entered and the product data shown. Check product labels and your supplier before you buy.
Source: [1]
The allowance adds the extra loose volume that equals FHWA's reduction in volume for a new gravel road layer. FHWA gives that figure for gravel roads, so it is context, not a figure for soil. New Mexico gives the same factor for top soil and for fill dirt.
What topsoil is
Utah State Extension defines topsoil by its place in the soil profile, not by a sale label, and says what is sold under that name does not always match.
Topsoil is defined as the A horizon only, while the E, B and C horizons compose the subsoil. Subsoil horizons have higher levels of clay, salts and lime than topsoil.
In Utah, topsoil layers commonly range from two to ten inches thick. Many materials sold as topsoils, particularly those from pits, are in fact subsoils.
Penn State Extension gives a minimum of 4 in[3] to 6 in[3] of good-quality topsoil, firmed or settled depth, to establish good-quality turf; the table uses both depths.
What fill dirt is
"Fill dirt" has no standard definition in the sources opened, so no definition is claimed here. UC ANR uses "fill soil" for subsoil used in cut-and-fill construction. The New Mexico table lists fill dirt as a material of its own beside top soil, at 0.8 ton/yd³[1] and 0.8 ton/yd³[1].
There are properties of subsoil however that make it suitable for other uses such as a source of “fill soil” for “cut-and-fill” construction operations
What garden soil is
"Garden soil" is a product name, and the extension sources opened do not define a bagged product by it. University of Maryland Extension describes ideal garden soil, says what bags labelled "organic soil" typically hold, and says topsoil sales are not regulated in Maryland.
Ideal garden soil is loose, deep, and crumbly. It holds water for root uptake and allows excess rainfall to percolate downward quickly.
The bags of “organic soil” you may see for sale typically don’t actually contain topsoil (i.e. mineral soil with clay, silt, and sand particles). These products contain various combinations of wood waste, bark fines, compost, peat moss, and other organic materials.
Topsoil sales are not regulated in Maryland.
What the compaction allowance does to the order
FHWA says ordinary compaction of a new gravel layer in many parts of the country reduces its volume by 30%[6] or more. Ordering loose material for a depth measured after compaction means ordering more than the volume you measure, which is the difference between the last two columns of the table.
Material in the stockpile or in trucks is very loose and has very low density. ... In many parts of the country this will result in 30 percent or greater reduction in volume.
Questions
What is the difference between topsoil and fill dirt?
Utah State Extension defines topsoil as the A horizon, the surface layer, and says many materials sold as topsoil are in fact subsoils. Fill dirt has no standard definition in the sources opened; UC ANR uses fill soil for subsoil used in cut-and-fill construction.
Can I grow grass in fill dirt?
The sources opened do not describe fill dirt as a lawn base. Penn State Extension says good-quality topsoil, firmed or settled, is needed to establish good-quality turf, and Utah State Extension says subsoils hold more clay, salts and lime than topsoil. Ask the supplier what is in the load.
How deep does topsoil go under a lawn?
Penn State Extension gives a minimum depth of good-quality topsoil, firmed or settled, for establishing turf. Its lower and upper depths are the first two rows of the table.
Which do I order by the yard?
The New Mexico table converts cubic yards to tons for both top soil and fill dirt, so either is counted in cubic yards. The table gives the yards for the example with and without an allowance for compaction; the dirt calculator does the same for your own sizes.
Calculate it for your project
Enter your own sizes to get the amount to buy or the layout figures, with the working shown and a page to print.
Try your own spot in the dirt calculatorSources (6)
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Conversion Factors for Construction Materials and Common Minerals (opens in new tab), New Mexico Energy, Minerals and Natural Resources Department, Mining and Minerals Division, undated one-page table, adapted from BLM H-3890-1 Handbook for Mineral Examiners.
Code or government.
“To convert cubic yards to short tons, multiply the commodity production cubic yardage by the conversion factors listed below. ... Base course 1.25 ... Fill Dirt 0.8 ... Gravel ¼" – 2" 1.42 ... Sand 1.45 ... Top Soil 0.8”
Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 1) -
Topsoil Quality Guidelines for Landscaping (opens in new tab), Utah State University Extension, published December 2010 (peer-reviewed fact sheet).
Code or government.
“Topsoil is defined as the A horizon only, while the E, B and C horizons compose the subsoil. Subsoil horizons have higher levels of clay, salts and lime than topsoil.”
“In Utah, topsoil layers commonly range from two to ten inches thick. Many materials sold as topsoils, particularly those from pits, are in fact subsoils.”
Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 2) -
Lawn Establishment (opens in new tab), Penn State Extension, web article, updated September 19, 2025.
Code or government.
“Typically, a minimum of 4 to 6 inches (firmed or settled depth) of a good-quality topsoil is needed to establish good-quality turf.”
Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 3) -
What is subsoil and how does it help a garden? (opens in new tab), UC Agriculture and Natural Resources (The Stanislaus Sprout, UC Master Gardener blog), published December 5, 2022, modified August 13, 2026.
Code or government.
“There are properties of subsoil however that make it suitable for other uses such as a source of “fill soil” for “cut-and-fill” construction operations”
Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 4) -
Soil to Fill Raised Beds (opens in new tab), University of Maryland Extension (J. Traunfeld), updated November 6, 2024.
Code or government.
“Ideal garden soil is loose, deep, and crumbly. It holds water for root uptake and allows excess rainfall to percolate downward quickly.”
“The bags of “organic soil” you may see for sale typically don’t actually contain topsoil (i.e. mineral soil with clay, silt, and sand particles). These products contain various combinations of wood waste, bark fines, compost, peat moss, and other organic materials.”
“Topsoil sales are not regulated in Maryland.”
Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 5) -
Gravel Roads Construction & Maintenance Guide (FHWA-OTS-15-0002), Section 3.19 Calculating Quantity (opens in new tab), Federal Highway Administration / South Dakota LTAP (K. Skorseth), August 2015; guide p. 71.
Code or government.
“Material in the stockpile or in trucks is very loose and has very low density. ... In many parts of the country this will result in 30 percent or greater reduction in volume.”
Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 6)
These are summaries of what the sources say, not professional advice. Codes and product data change. Check with your building department and the product label about your own project.