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.
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-cluster 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?
For 720 sq ft × 5″ deep, the exact volume is 11.11 cubic yards (720 × 0.4167 = 300 ft³, divided by 27). With the default 8% waste cushion that rounds up to 12.0 yd³ as the practical order — the cushion accounts for transit settling, soil-density variation, and germination compaction. That's the same math behind the homepage anecdote: 11 yd³ exact, 12 yd³ ordered, the extra cubic yard became a raised bed in the south corner.
How deep should topsoil be for a new lawn?
4 inches is the industry default for new-lawn establishment from seed or sod, with 6″ specified on rough graded subsoil. This range tracks landscape-supplier consensus and matches what most cooperative-extension lawn-establishment guides assume — though the extension publications themselves typically focus on seedbed prep + soil amendments rather than prescribing a topsoil depth. The calculator's 'New lawn' preset uses 4″.
How thin should topsoil be for overseeding?
¼ to ½ inch — a top-dressing layer, not a fresh establishment depth. Anything thicker risks burying existing turf and stalling germination. The calculator's 'Overseed' preset uses 0.5″ as a conservative default; ¼″ is a tight top-dressing for thin spots, ¾″ is the upper end for filling minor depressions before reseeding. Don't pile topsoil on living grass thinking more is better — it isn't.
How many 40 lb bags of topsoil are in a yard?
27 bags at 1 cu ft per bag (the typical loose yield), or 36 bags at 0.75 cu ft (the denser compressed-screened yield). Real-world bags vary 0.5-1 cu ft depending on supplier and moisture content, so the calculator surfaces both numbers — pick whichever matches your actual bag spec. Above 1 cubic yard, bulk delivery almost always beats bagged on cost; below the supplier's 3 yd³ residential minimum, bagged is usually the only option even when it's pricier per yd³.
Why is the waste cushion 8% instead of 5%?
Topsoil settles more in transit than concrete does, soil density varies with moisture (a 'cubic yard' delivered wet weighs and compacts differently from one delivered dry), and germination + watering compacts the spread surface another fraction once it's down. 8% absorbs all three. The cushion bumps to 12% on 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 is almost always cheaper than bagged on a per-cubic-yard basis (you save 30-50%). Below 1 yd³, bagged usually wins because the supplier's delivery fee + the typical 3 yd³ bulk minimum erodes the savings. The awkward middle is 1-3 yd³: bulk is cheaper per yd³ but most Chicago-suburb suppliers won't deliver under 3 yd³ without a short-load fee, so you're stuck either with bagged or finding a smaller-minimum supplier. The calculator flags this with a 'below supplier minimum' warning.
Related guides
- How much topsoil for overseeding →
- Topsoil per square foot for grass →
- How much topsoil for grass to grow →
- Concrete yardage calculator (sister cluster) →
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.