Key takeaways
- One formula sizes any job: square feet times depth in inches, divided by 324, equals cubic yards.
- Topdressing an existing lawn wants a quarter to a half inch per pass, never more.
- A new lawn or sod bed wants good soil worked into the top six inches, which is a bulk order rather than a bag order.
- Colorado State University advises against adding topsoil over grass seed after you've sown it, which is the opposite of common advice.
- Screened topsoil costs more than unscreened and is worth it on any surface you'll mow, since rocks find mower blades.
- Topsoil, lawn soil, and garden soil are three different products, and only one of them belongs under sod.
Most topsoil orders are wrong by a factor of three, in both directions. People buy eight bags for a job that needs a truckload, or a truckload for a job that needs eight bags. Neither mistake is cheap.
Sizing topsoil for lawn work isn't complicated once you've seen the arithmetic once. There's a single formula, four depths worth memorizing, and one decision about screening. That's the whole thing. Below we'll size a job from scratch, cover how deep to go for sodding versus seeding versus repair, and sort out the topsoil-versus-lawn-soil confusion the bagged brands have created. Our Top Soil collection is stocked in Glenwood Springs if you want to price it as you read.
How much topsoil do you need? One formula covers every job
A cubic yard is 27 cubic feet, and spread one inch deep it covers 324 square feet. That single number does all the work:
Cubic yards = (square feet x depth in inches) / 324
Measure the area, pick your depth, run the numbers. Colorado State University's soil amendment guidance lands in the same place, noting that three cubic yards covers 1,000 square feet approximately one inch deep. Here's that math already done for a 1,000 square foot area, which you can scale up or down:
| Depth | Job | Cubic yards | 1 cu ft bags |
|---|---|---|---|
| 1/4 inch | Topdressing established turf | 0.8 | 21 |
| 1/2 inch | Heavy topdress or minor leveling | 1.5 | 42 |
| 1 inch | Leveling low areas | 3.1 | 84 |
| 2 inches | Repair and fill | 6.2 | 167 |
| 6 inches | New lawn or sod bed prep | 18.5 | 500 |
How deep should topsoil be for sodding, seeding, and topdressing?
Depth is where most projects go wrong, and the right answer changes completely depending on the job. CSU recommends cultivating amendment into the top six inches for lawn applications, and that's the benchmark for anything you're building from scratch.
- Sodding: six inches of prepared soil underneath. Sod arrives with maybe half an inch of soil attached to the roots. It has nowhere to go unless what's beneath it holds water and lets roots down.
- New seedbed: the same six inches, worked in before you sow. Mix the topsoil into the existing soil rather than laying it on top as a separate layer, or you create a texture boundary roots stall at.
- Topdressing an established lawn: a quarter to a half inch per pass. Grass has to grow through it. Bury the crowns and you'll kill the turf you're trying to improve.
- Filling low spots: apply half an inch at a time, repeated. Two passes a month apart beats one deep fill that smothers everything under it.
- Around a large tree: don't. Piling soil over surface roots or against the trunk suffocates the tree slowly. Grade away from it and accept the dip.
One correction worth making, because most guides get it backwards: CSU is explicit that adding topsoil or sand after seeding is not recommended. Prepare the soil first, then sow the grass seed onto it and keep the surface moist. Burying new grass seed under a layer of topsoil is one of the most common reasons a reseed comes up thin.
Topsoil vs lawn soil vs garden soil
These three get used interchangeably at garden centers and they shouldn't be. Topsoil isn't just dirt with a better name. It's the base material, mineral soil that's been screened and sometimes blended with organic matter, and it's what you use in volume when you need to build grade or improve the existing soil before planting.
Lawn soil is topsoil with fertilizer and seed-holding additives mixed in, commonly sold in small bags at a much higher price per cubic foot. It's convenient for a patch job and uneconomic for anything larger. Garden soil is richer still, built for flowers, flower beds, and vegetable gardens, and too high in organic matter to sit under a lawn where it'll settle and leave dips a year later.
So the best topsoil for grass is usually the plainest one. For sodding and lawn repair, plain screened topsoil is the right product, and you enrich it separately with compost or a starter fertilizer, adding nutrients in addition to the soil itself. That way you control the rate instead of paying for whatever the bag decided you needed.
Screened topsoil vs unscreened
Screening pushes soil through a mesh to pull out rocks, roots, and clumps. Unscreened material is cheaper per yard and fine where it'll be buried, such as backfill or building rough grade behind a wall.
On anything you'll mow, screened topsoil earns the difference. Rocks work their way up through a lawn every freeze-thaw cycle, and they find mower blades eventually. Screening also helps with a second problem: unscreened soil commonly carries weeds along with the clumps, and it spreads unevenly, which makes leveling frustrating work.
Our Mountain West Top Soil is a 3/8 inch minus screened blend of bark, peat moss, and native soils, which is fine enough to rake into a seedbed or work through turf when topdressing lawn areas. The texture is the point: soil that size spreads level, settles evenly, and doesn't leave stones sitting proud of the surface. It's the same material we send out across the landscapes we supply on the Western Slope, for lawns and planting beds alike.
Bags, pallets, and getting it to the site
Mountain West Top Soil comes in 1 cubic foot bags at 25 pounds each, or on pallets of 60. A full pallet is about 2.2 cubic yards, which covers roughly 720 square feet at an inch deep, or a bit over 2,800 square feet as a quarter-inch topdressing.
Match the format to the job. Bags make sense for topdressing, patching, and anything you're carrying through a gate by hand. Once you're past a few yards, pallets and bulk are the only sane option, and it's worth ordering the soil at the same time as the bluegrass sod so both land on site the same week rather than sod sitting on a pallet waiting for a seedbed. Understand the volume before you book the delivery and the rest of the project runs on schedule.
