How I'd actually use this on a flip
The first time the topsoil math earned its keep was a Spring 2021 order at a Chicago-suburb gut rehab — the cedar deck was finished, the south-yard regrade was done, and the lawn needed to come back before staging photos. The math came back as 11 cubic yards. I ordered 12. The extra yard turned into a raised bed in the south corner with mulched borders and three tomato plants — that bed ended up in the listing photos and probably moved the asking price a thousand bucks.
That order taught me the difference between “exact math” and “what the supplier actually backs into your driveway.” A “cubic yard” of topsoil delivered loose settles 5-15% in transit — what the supplier scoops at the yard isn't what arrives. Wet soil weighs more and packs denser; dry soil arrives fluffier and spreads further. The 8% default cushion absorbs the variance; 12% is what I use on rough graded sites where the depth varies more than half an inch across the spread.
On the “when not to over-order” side, topsoil isn't concrete. It degrades. If a pile sits 4-6 weeks before you spread, weed seeds germinate in it, organic matter oxidizes, and the surface compacts into a crust. Better to schedule a second delivery for the next phase than to stockpile. Below the supplier's 3 yd³ residential minimum, this is moot anyway — you're stuck with bagged either way.
Topsoil, compost, or blend?
Three bulk-material types show up at the landscape-supplier counter for the jobs above. The differences matter more than the labels suggest:
Screened topsoil.Fine particles, no rocks or sticks, roughly neutral pH. The workhorse for lawn work — new lawn install, overseed top-dress, patch repair, leveling. Builds a consistent seedbed and doesn't push existing turf into a growth spike.
Compost or compost-rich blend.High organic matter, high nutrients. Right for vegetable beds and amending nutrient-poor soil. I wouldn't reach for straight compost as the default lawn layer unless a soil test or local cooperative-extension advice points that way — the nutrient load is rich for a top-dressing.
Topsoil/compost blend (often sold as “garden mix” or “lawn mix”). A middle ground — usually 70-80% screened topsoil with 20-30% compost mixed in. The ratio matters: a 70/30 blend behaves differently than a 50/50. Ask the supplier for the actual ratio before ordering — “lawn mix” isn't a standard term and varies yard to yard.
My default is plain screened topsoil for lawn work and a 70/30 blend for vegetable beds. For flower beds and amendment cases where the underlying soil might be struggling, spend $15 on a soil test before ordering blend or amendment. The overseed guide has the longer treatment for lawn-specific cases.
Where this number breaks down
A few traps that put the math on the wrong side of the order:
- Wet vs. dry delivery weight.A “yard” of saturated topsoil weighs 2,400+ lb; the same volume dry weighs ~1,800 lb. Suppliers price by volume, but volume measured wet is different from volume measured dry. If your driveway sees a wet delivery, expect more compaction once it spreads.
- Screened vs. unscreened (fill) dirt.Screened topsoil costs 2-3× more per yard but is what you want under sod or a seed bed. Unscreened fill is fine for under-grade leveling where you'll cap with screened on top. Suppliers conflate the two when you call by phone — confirm which you're ordering.
- Subgrade compaction. The math assumes the depth is uniform across the area. A subgrade with 1-2″ dips swallows mix into the dips before the surface comes up flat. The 8% default cushion absorbs minor variation; rougher sites need 12%.
- The 1-3 yd³ trap.Above 1 yd³, bulk is cheaper per yard than bagged. Below 3 yd³, most Chicago-suburb suppliers won't deliver bulk without a short-load fee. So a 1.75 yd³ order is in awkward territory — you'll either pay the bag premium or hunt for a smaller-minimum supplier. Plan around it.
- Storage perishability.Topsoil in a pile for more than 4-6 weeks degrades. Don't over-cushion thinking you'll use the extra later — schedule a second delivery instead.
Methodology
Every number on this page traces to one of three layers — site arithmetic for the volume math, landscape-supplier conventions for bag yields and bulk minimums, and cooperative-extension guidance for seedbed prep + soil-amendment practices. The per-calculator sourcing tier in methodology spells out which sources back which kinds of claims. Depth values are framed as industry consensus — the cooperative-extension publications back what they cover (seed depth, watering depth, seedbed prep), not the topsoil-spread depths shown here.
Show the formulas
- Volume:
(L ft × W ft) × (D″ / 12) / 27= cubic yards. - Practical order: exact × (1 + waste%/100), rounded UP to the next 0.25 yd³ for Chicago-suburb residential dispatch. Half-yard suppliers add one further step.
- Bag count, 1 cu ft loose (40 lb typical US):
ceil(exact yd³ × 27)= 27 bags / yd³. - Bag count, 0.75 cu ft compressed-screened:
ceil(exact yd³ × 36)= 36 bags / yd³. - Below-bulk-minimum flag: triggers when practical < 3 yd³ (typical Chicago-suburb residential minimum).
Frequently asked
How much topsoil do I need for a 720 sq ft lawn at 5″ deep?
About 12 cubic yards delivered. 11.11 yd³ exact, rounded to 12 with the cushion that absorbs settling and density variation. The math: 720 × (5/12) = 300 cu ft. Divided by 27 gives 11.11 yd³ exact. With the default 8% waste cushion, the practical order is 12.0 yd³. In practice: That's the order behind the homepage anecdote — 11 yd³ exact, 12 yd³ ordered, the extra cubic yard became a raised bed in the south corner that ended up in the listing photos.
How deep should topsoil be for a new lawn?
4 inches over prepared soil; 6 inches over rough graded subsoil. When 4″ is enough: Existing yard, mostly level, you're spreading on top of cleaned and amended grade for seed or sod. When you want 6″: Fresh build site, rough graded subsoil, or significant compaction below — the deeper bed gives roots room and resists rutting. The calculator's “New lawn” preset uses 4″.
How thin should topsoil be for overseeding?
¼ to ½ inch — a top-dressing, not a fresh establishment depth. Use ¼″ for: Tight top-dressing on thin spots, without burying the existing turf. Use ½″ for: The calculator's preset default — a conservative top-dress that still lets the existing grass breathe. Use ¾″ (max) for: Filling minor depressions before reseeding. Don't go thicker: More isn't better. Anything over ¾″ on living grass risks burying it and stalling germination.
How many 40 lb bags of topsoil are in a yard?
27 bags at 1 cu ft each (loose-yield) or 36 bags at 0.75 cu ft each (denser screened-yield). Real bags vary between 0.5 and 1 cu ft depending on supplier and moisture content. Buy bulk when: Project needs more than 1 cubic yard AND the supplier will deliver, since bulk almost always beats bagged on cost above the 1 yd³ break. Use bags when: Project is under 1 yd³, access is too tight for a delivery truck, or you can't meet the supplier's 3 yd³ residential minimum. The awkward middle: 1-3 yd³ — bulk is cheaper per yard, but most Chicago-suburb suppliers won't deliver under 3 yd³ without a short-load fee.
Why is the waste cushion 8% instead of 5%?
Three things compress the spread between what the supplier loaded and what ends up under your grass — settling in transit, moisture variation, and germination compaction. 8% absorbs all three. Settling: Topsoil settles more in transit than concrete does — a loose-loaded yard at the supplier yard isn't a yard in your driveway. Moisture: A “cubic yard” delivered wet weighs more and packs denser than the same volume delivered dry. Spread compaction: Watering and germination compress the surface another fraction once it's down. When to bump to 12%: Rough graded sites where the spread depth varies more than ±0.5″ across the area.
Should I order bulk delivery or bagged topsoil?
Above 1 cubic yard, bulk almost always beats bagged on cost (30-50% savings per cubic yard). Below 1 yd³, bagged usually wins. Buy bulk when: Project is over 1 yd³ AND you can meet the supplier's 3 yd³ minimum (or you're ordering 3+ anyway). Use bags when: Project is under 1 yd³, OR access is too tight for a delivery truck, OR you can't meet the supplier minimum and the short-haul fee erodes the bulk savings. The 1-3 yd³ trap: Bulk is cheaper per yard, but most Chicago-suburb suppliers won't deliver under 3 yd³ without a short-load fee — you're stuck either bagged or hunting for a smaller-minimum supplier. The calculator flags this with a “below supplier minimum” warning.
What I'd do next
- Topsoil depth for a new lawn
New install at 4-6″. Screened vs unscreened, and where the stockpile-quality trap costs you.
- Per square foot for irregular yards
When the yard isn't a clean rectangle. Plus the bag-vs-bulk breakpoint by area.
- Topdressing for overseeding
Existing lawn rehab at ¼-½″. Different math, different cushion, different timing.
By James Wu. Volume math is site arithmetic, formulas shown above. Bag-volume conventions follow landscape-supplier practice (40 lb bags vary 0.5-1 cu ft depending on moisture and screening). Seedbed prep and watering-depth context (cited where the page touches lawn establishment) from UC Agriculture & Natural Resources Healthy Lawns — Planting from Seed and University of Minnesota Extension — Seeding and Sodding Home Lawns. Topsoil-spread depth values are framed as industry consensus — cooperative-extension publications cover seedbed prep + soil amendments rather than prescribing a topsoil-spread depth. Residential bulk-delivery minimums and short-load conventions reflect Chicago-suburb landscape-supplier practice. Engine logic in lib/sitework/topsoil.ts. Not landscape-design or horticultural advice — for soil-amendment decisions specific to your site, work with a local cooperative-extension agent. Full methodology.