WSDOT 9-14.2, where two of three topsoil types are defined by provenance
Aggregate is specified to death: gradation, wear, fracture faces. Topsoil is not. WSDOT defines it in three types, two of them by where it was dug rather than what is in it, and the third as whatever the job documents say. The only universal numeric requirement in the entire section is that stones stay under two inches and under a tenth by volume. Topsoil is a provenance label, not a specification, and that is why nobody can tell you what it weighs or how far it will settle.
Topsoil volume and settlement
ft
ft
ft
in
%
cu ft
lb/cu ft
The allowance here is for settlement, not compaction. Topsoil must not be compacted: the pore space is the point of it.
Specification summary
Generated from on .
Reopen that address to reproduce these figures exactly.
Entered
Result
Delivery day against a month later
Worked example
A 30 ft by 20 ft bed at a finished 6 in, with a 15% settlement allowance, bought in bulk.
Area. 30 × 20 = 600 sq ft.
Finished volume. 600 × 6/12 = 300 cu ft = 11.11 cu yd.
Settlement. 15% on top: 12.78 cu yd to order.
Fill to.6.9 in on delivery day, to finish at 6.
Weight. Not calculated. Topsoil is sold by volume and its density moves with organic content and moisture.
Do not compact it. The pore space is what you paid for.
The fill-to figure is the one to write on your hand. Level on delivery day is low a month later, and the difference on a 6 inch bed is nearly an inch, which is the difference between a bed that looks right and one that looks sunken against the path. Mound it and let it come down.
The formula
Volume, and one allowance that runs the opposite way to gravel:
V = A × d/12 order = V(1 + s) fill to = d(1 + s)
A, d
area in sq ft and FINISHED depth in in, after settlement
s
settlement allowance. Ours, defaulting to 0.15, higher for compost-rich soil
fill to
the depth to leave on delivery day, which is more than the finished depth
27
cubic feet in a cubic yard
On the gravel page the allowance covers volume a compactor removes. Here it covers volume that leaves on its own, and the two must not be confused: compacting topsoil deliberately is the one thing you should never do to it.
What you are actually buying
Ring a landscape yard and ask for topsoil and you will get a price per yard without anybody asking what for. That is not sloppiness on their part, because the word does not carry a specification that would let them ask a useful question.
WSDOT, which specifies aggregate down to fracture faces and Los Angeles wear, defines topsoil in three types. Type B is soil dug from within the project. Type C is the same thing dug somewhere else. Type A is whatever the job's Special Provisions say it is. The section's only universal numeric requirement is that stones stay under two inches and under a tenth of the volume.
That is a state highway department, in a document that leaves nothing to chance elsewhere, describing topsoil essentially by where it came from.
So the practical questions are the ones nobody thinks to ask. Is it screened, and to what. Has compost been blended in, and how much. Where was it dug. What was growing on it. Those determine how it behaves and how far it settles far more than the word on the invoice does.
The three types, and what each one actually specifies
Type
What the specification says
What that amounts to
Type A
As specified in the Special Provisions.
The spec declines to define it. Whatever the job documents say it is.
Type B
Native topsoil taken from within the project limits either from the area where roadway excavation is to be performed or from strippings from borrow, pit, or quarry sites, or from other designated sources. All vegetative matter, less than 4 feet in height, shall become a part of the topsoil.
Defined by where it came from, not by what is in it.
Type C
Native topsoil meeting the requirements of Topsoil Type B but obtained from a source provided by the Contractor outside of the Contracting Agency owned right of way.
Type B from somewhere else. Again, provenance.
Read 2026-09-08. Quoted from WSDOT section 9-14.2. The third column is this page reading the second.
Even a state DOT will not tell you what topsoil is
Aggregate is specified to death: gradation, wear, specific gravity, fracture faces. Topsoil is not, and the gap is startling once you look for it.
WSDOT specifies topsoil in three types. Read what they actually say:
WSDOT Standard Specifications section 9-14.2
Type
What the specification says
What that amounts to
Type A
As specified in the Special Provisions.
The spec declines to define it. Whatever the job documents say it is.
Type B
Native topsoil taken from within the project limits either from the area where roadway excavation is to be performed or from strippings from borrow, pit, or quarry sites, or from other designated sources. All vegetative matter, less than 4 feet in height, shall become a part of the topsoil.
Defined by where it came from, not by what is in it.
Type C
Native topsoil meeting the requirements of Topsoil Type B but obtained from a source provided by the Contractor outside of the Contracting Agency owned right of way.
Type B from somewhere else. Again, provenance.
Two of the three are defined by where the material came from. Not what is in it, not how much organic matter, not pH, not texture. Where it was dug. And Type A, the one you would expect to carry the actual specification, is defined as whatever the job's own documents say.
The only universal numeric requirement in the whole section is this:
Topsoil shall not contain recycled materials, foreign materials, or Noxious and Nuisance weeds of any Class designated by authorized State or County officials. Aggregate shall not comprise more than 10 percent by volume of Topsoil and shall not be greater than two inches in diameter.
No stones over two inches, no more than a tenth of it aggregate, no weeds, no rubbish. That is the entire objective standard, from the most rigorous document that bothers to mention topsoil at all.
Which is the honest answer to why a topsoil calculator cannot give you a weight, a nutrient content or a settlement figure. The word is a provenance label, not a specification, and at a landscape yard it is looser than this.
Depth, and what it is actually for
Depth is a growing decision rather than an engineering one, and this page takes whatever you give it. What is worth knowing is what each depth buys.
A thin layer holds turf and not much else. Grass roots will run through it into whatever is underneath, so a thin skim over compacted builder's subsoil produces a lawn that browns off in the first dry spell, because the roots hit a pan and stop.
Beds want depth because roots want depth. A perennial bed at the same depth as a lawn is a bed that needs watering constantly.
Raised beds are a container. Whatever depth you build is the entire root zone, and it will settle more than a bed on open ground because there is no existing soil for it to knit into.
The one place depth is nearly an engineering question is over a new build, where the subsoil has been driven on by plant for months. Adding topsoil on top of a compacted pan without breaking the pan first buys you a bath rather than a bed.
Bags against bulk, and where the line is
Bagged soil is sold by volume in cubic feet, which is convenient: no density, no scale, no delivery. It is also several times the price per cubic yard of bulk.
A cubic yard is 27 cubic feet, so it is eighteen bags at 1.5 cu ft or twenty-seven at 1. A modest 8 by 4 raised bed at 12 inches deep is a cubic yard and a half, which is twenty-six bags. That is a car full, twice.
The crossover is usually around a yard. Below that, bags win on hassle. Above it, the price difference gets hard to justify and a delivery is one decision instead of forty.
The other consideration is that bulk soil arrives as a heap on your drive and has to be moved by barrow, and a cubic yard is a bit over a ton of barrowing.
What this page will not tell you
Weight, unless you supply a density. Topsoil density moves with organic content and with how wet it is on the day, more than aggregate does, and it is normally sold by volume anyway so the number rarely matters.
Nutrient content, pH or texture. None of those follow from the word topsoil, and a soil test costs very little compared with a bed that does not grow anything.
How much it will really settle. The default here is ours. A mineral-heavy screened soil moves less; a compost-rich blend moves a lot more, because compost is still decomposing and loses volume as it does.
Whether you need it at all. Improving the soil already on site is often better and always cheaper than importing a layer on top of it.
Topsoil settles, and it is the one material you must not compact
Gravel gets compacted and the allowance is for the volume the compactor removes. Topsoil is the exact opposite and the arithmetic runs the other way.
Compacting topsoil destroys the thing you bought it for. Its value is the pore space: room for air, water and roots. Drive a plate compactor over it and you have expensive subsoil.
But it still settles, on its own, over weeks, as it is watered and as the organic fraction breaks down. So a bed filled level on delivery day is a bed that is low a month later, and the allowance exists for that rather than for compaction.
How much depends on how organic the material is and how it was handled, and it is not a figure this page will publish. It is an input, it defaults to a round 15%, and it is labelled as ours. A mineral-heavy screened soil settles less; a compost-rich blend settles considerably more, because the compost is still decomposing.
The practical version: overfill raised beds and mound the surface. Filling level on day one is filling low.
The source, and what it does not cover
Read 2026-09-08. 2027 Standard Specifications M 41-10, Division 9 Materials, Washington State Department of Transportation, section 9-13.1(2). Sizes riprap by weight and volume together, which is the only place found that pins a stone's weight to its volume in a government publication. Both equivalences give about 149 lb per cubic foot, which is SOLID rock rather than a loose pile.
That document sets minimum properties for engineered aggregates: gradation, degradation factor, Los Angeles wear, specific gravity. What it does not contain, and what no government publication found from here contains, is a table of typical loose densities for the materials sold at a landscape yard. The specifications describe what a product must achieve, not what a heap of it weighs.
Which is the honest answer to why every gravel calculator's tonnage figure is uncited. There is nothing to cite.
Frequently asked questions
How much topsoil do I need for a 30x20 bed?
At a finished 6 in, 300 cubic feet, which is 11.11 cubic yards. Add a settlement allowance on top: at 15% you would order 12.78 cubic yards and fill to about 6.9 inches on delivery day so it finishes at 6.
How much does a yard of topsoil weigh?
It depends on the organic content and how wet it is, and this page will not guess. Topsoil is normally sold by volume rather than weight for exactly that reason. If your supplier does sell by the ton, ask them for their density: they are the ones weighing it.
Should I compact topsoil?
No. The value of topsoil is its pore space, room for air, water and roots, and compacting it removes exactly that. What you get is expensive subsoil. It will settle on its own over a few weeks, which is what the allowance on this page is for.
How much does topsoil settle?
Enough to matter and not a figure anybody publishes. The default here is 15% and it is this page's own number. A screened mineral soil settles less; a compost-rich blend settles considerably more because the compost is still decomposing. Fill proud and let it come down.
How many bags of topsoil in a cubic yard?
Eighteen bags of 1.5 cubic feet, or twenty-seven bags of 1 cubic foot, since a cubic yard is 27 cubic feet. Bagged soil costs several times bulk per yard, so the crossover is usually around one yard: below that bags win on convenience, above it a delivery makes more sense.
What is the difference between topsoil and garden soil?
Nothing standardised, which is the problem. Even WSDOT's specification defines two of its three topsoil types by where the material was dug rather than what is in it, and the third by reference to the job's own documents. Ask the supplier whether it is screened, whether compost has been blended in, and where it came from.
How deep should topsoil be for a lawn?
That is a growing question rather than a code one and this page takes whatever depth you specify. The thing worth knowing is that a thin layer over compacted subsoil gives roots nowhere to go, so breaking up what is underneath usually matters more than adding depth on top.
Check these numbers yourself
2027 Standard Specifications M 41-10, Section 9-14.2 TopsoilWashington State Department of Transportation. Specifies topsoil in three types, two of them by provenance and one by reference to the job's own Special Provisions. The only universal numeric limit in the section is aggregate under 10% by volume and under two inches.
How every figure here is verified: Sources & Method. Who builds this: About. Found something wrong? Tell us and it gets fixed or removed.
Figures on this page last checked against the source documents on 2026-09-08. Codes are amended locally; confirm against the edition your jurisdiction enforces.
The settlement allowance is this page's own figure, not a standard. Nobody publishes one, because topsoil is not a specified material: WSDOT section 9-14.2 was read on 8 September 2026 and defines two of its three types by provenance. Depth, nutrient content and whether you need imported soil at all are growing decisions this page does not make. Do not compact topsoil.