Volume · Weight · Bags · Delivered Cost
Dirt Calculator
Enter your area dimensions, pick a material, and get an instant cubic-yard count with tons, truckloads, bag equivalents, and a delivered-cost estimate. Supports rectangles, slopes, circles, triangles, rings, and road sections — across multiple areas at once. Use it as a fill dirt calculator for grade-up and backfill, or as a topsoil calculator for the finishing layer.
Input Parameters
Quick presets
Area 1· Rectangle / Flat Area
✓ 20' 0" (240 in)
✓ 15' 0" (180 in)
✓ 0' 6" (6 in)
Material & Compaction
Cheapest bulk fill; may contain small rocks or clods
Loose dirt shrinks when spread and tamped — 15% is the recommended residential default.
Delivery & Bagging
Most residential deliveries
Standard big-box bag volumes — bag equivalents appear in results.
Cost & Deliveryoptional
Fill Dirt — Mixed / Unscreened: typically $5–$15/yd material only.
Unlocks a regional freight estimate for your area.
Flat fee for each truck — how most bulk yards quote
Your Estimate
Cubic yards to order
6.4
cu yd · includes +15% buffer · density 1.55 t/yd³
Base volume
5.56 yd³
150 ft³ before buffer
Weight
9.90 t
short tons · 1.55 t/yd³
Truckloads
1 × 10 yd³
Standard single-axle
Bag equivalent
173 bags
1.0 cu ft bag
Cubic feet
173 ft³
150 ft³ base · +15% buffer
Gallons
1,290 gal
planters & amendments
Budget estimate
Planning estimate only — confirm pricing with local suppliers.
Formula: L × W × D ÷ 27 = base cu yd. Buffer added on top. Weight uses product-specific density (115 lb/ft³). Circle/ring/road modes apply πr², π(R²−r²), and trapezoid cross-sections respectively.
Quick answer
How Much Dirt Do You Need?
Multiply length × width × depth (all in feet), then divide by 27 to get cubic yards. Always add a compaction buffer — 15% is the reliable default for residential work. A 20 × 15 ft area at 6 inches deep needs 20 × 15 × 0.5 ÷ 27 = 5.56 cu yd base, or 6.4 cu yd to order with the buffer. One cubic yard of mixed fill dirt weighs about 1.55 tons and covers 54 sq ft at 6 inches deep.
Step by step
How to Use This Dirt Calculator App
Five inputs drive every number in the results panel. Work through them in order and the figure you hand to a supplier already accounts for the two things most homeowners forget: compaction loss and the unit the yard actually bills in.
- 1
Measure each area separately
Take length and width in feet for every zone — front yard, side beds, driveway apron. Split L-shaped or odd lots into rectangles, circles, and triangles and add them as separate areas; the calculator totals them. Measure twice and round up slightly, because a 6-inch error across a 40 ft run changes the order by half a yard.
- 2
Set the finished depth, not the loose depth
Enter the depth you want after the dirt is spread and settled. On uneven ground use the average depth across the area. Typical residential values: 3–6 in for yard leveling, 6–12 in for foundation grade-up, 4–8 in for a garden-bed base, and 6–12 in for driveway subbase.
- 3
Pick the material you will actually receive
Fill dirt, screened fill, sandy fill, clay, and topsoil each carry their own density from about 1.0 to 1.72 tons per cubic yard. Selecting the right one fixes the tonnage line, the price range, and the compaction default in one step.
- 4
Choose a compaction buffer
Loose delivered dirt shrinks once it is spread and tamped, so the order has to exceed the measured hole. Use 10% for granular sand, 15% for general residential grading, and 20–25% for clay-heavy or structural fill placed to a compacted specification.
- 5
Read the order figure, then add logistics
The “order” number already includes the buffer — that is what you give the supplier. Truckloads round up because yards do not deliver fractional loads, and freight is quoted per load, per cubic yard, or per ton depending on the yard. Enter your ZIP and price to see a delivered range.
Ask for “clean fill” by name. It means no construction debris, trash, concrete chunks, stumps, or large roots — anything that will rot and leave a void later. Small rocks and clods are still normal in unscreened fill, which is why the surface layer is usually finished with screened material or topsoil.
The math
Dirt Volume Formula (How the Calculator Works)
Every dirt estimate starts as a volume problem: geometry first, conversions second. The number 27 converts cubic feet to cubic yards — one cubic yard is 3 ft × 3 ft × 3 ft = 27 cu ft. Depth measured in inches must be divided by 12 before multiplying.
Volume (cu yd) = L (ft) × W (ft) × D (ft) ÷ 27
Order = Base × (1 + buffer %) · Tons = cu yd × material density
Worked Example: 10 ft × 10 ft at 6 Inches
- Step 1. Convert depth: 6 in ÷ 12 = 0.5 ft
- Step 2. Volume: 10 × 10 × 0.5 = 50 cu ft
- Step 3. Convert: 50 ÷ 27 = 1.85 cu yd base
- Step 4. Add 15% buffer: 1.85 × 1.15 = 2.13 cu yd to order
- Step 5. Weight (mixed fill): 2.13 × 1.55 = 3.3 tons — one pickup load is ~1.25 tons, so plan a bulk delivery.
Dirt Calculator with Compaction: Why Add a Buffer?
Loose fill dirt shrinks when it is spread and tamped. A truck delivers cubic yards of fluffed material; once a plate compactor passes over it, the same dirt occupies a smaller volume. Order only the base calculation and your fill will finish below grade. Granular sandy fill compacts roughly 10–12%, general residential fill about 15%, and clay-heavy fill can shrink 20–25% from its loose delivered volume.
Volume states
Bank, Loose & Compacted: Why 10 Yards Isn't Always 10 Yards
Dirt changes volume three times between the ground and the finished grade. Suppliers quote in different states, so mixing them up is the most common reason a job comes up short. Here is what each one means.
| State | What it means | Volume change |
|---|---|---|
| Bank (Bcy) | Dirt sitting naturally in the ground before anyone digs it. Survey volumes and cut-and-fill takeoffs are measured in bank yards. | 1.00 — baseline |
| Loose (Lcy) | The same dirt after excavation and loading. Air gets trapped between clods, so it fluffs up. This is the state it arrives in on a dump truck. | ≈ +10–25% swell |
| Compacted (Ccy) | Dirt after spreading, watering, and tamping in lifts. Air is forced out and the material densifies. This is the depth you actually keep. | ≈ −20% shrink from loose |
The 20% rule of thumb
If the fill will be compacted with a plate or roller — and structural fill should be — order 20–25% more loose dirt than the measured hole. Leftover dirt is cheap; a second delivery to fetch the last yard and a half is not. For non-structural garden and landscape fill, 10–15% is usually enough.
Swell factor varies by soil
Granular sand and gravel swell about 10–15%; loam and mixed fill 15–25%; heavy clay can swell 25–35% because it breaks into large, airy clods. Shrink on compaction runs in the opposite direction — sandy material consolidates least, clay the most. That is why the buffer is adjustable instead of fixed.
Planning shortcut: measured hole (compacted) × 1.25 ≈ loose yards to order for structural fill; × 1.10–1.15 for landscape fill. Then convert loose yards to tons with the material density — never convert compacted volume directly to tons.
Geometry
Six Shape Modes, One Calculator
Real projects are rarely one clean rectangle. Pick the shape that matches each zone — or add several areas and let the calculator total them.
Rectangle / Flat Area
L × W × D ÷ 27
A 40 × 20 ft backyard filled 6 in deep: 40 × 20 × 0.5 ÷ 27 = 14.8 cu yd base.
Best for: Yard leveling, garden beds, foundation grade-up, pads
Slope / Wedge
(L × W × D) ÷ 2 ÷ 27
A 40 × 20 ft slope 18 in deep at the low end: (40 × 20 × 1.5) ÷ 2 ÷ 27 = 22.2 cu yd.
Best for: One edge at grade, tapering to a maximum depth at the far edge
Circle
π × (d ÷ 2)² × D ÷ 27
A 12 ft diameter round bed 4 in deep: π × 36 × 0.333 ÷ 27 = 1.4 cu yd.
Best for: Round beds, tree rings, fire-pit pads, post and pole holes
Triangle
(b × h ÷ 2) × D ÷ 27
A corner bed with 15 ft base, 10 ft height, 6 in deep: 37.5 cu ft = 1.4 cu yd.
Best for: Lot corners and odd-angled beds rectangles can't model
Ring / Donut
π × (R² − r²) × D ÷ 27
A ring bed 10 ft outside ⌀ with a 4 ft tree circle, 8 in deep: 4.9 cu yd.
Best for: Donut beds around trees, pools, and patio islands
Road / Trench Section
((Wt + Wb) ÷ 2) × D × L ÷ 27
A 200 ft lane, 12 ft top / 10 ft base, 4 in avg: 200 × 11 × 0.333 ÷ 27 = 27.1 cu yd.
Best for: Driveway subbase, private lanes, and ditch regrade sections
Fill Dirt Calculator on Slope Ground
On sloped ground the fill tapers from zero at the high edge to full depth at the low edge, so a flat L × W × D reading over-orders by nearly half. Select the Slope shape and enter the maximum depth at the low side — this fill dirt calculator on slope ground applies the average-depth method, (L × W × D) ÷ 2 ÷ 27, so a 40 × 20 ft yard tapering to 18 in at the low end needs 22.2 cu yd, not the 44.4 cu yd a flat reading suggests. Ground that falls in two directions should be split into two slope areas and totaled.
Density reference
Dirt Calculator Weight & Tons by Material
One cubic yard of dirt weighs roughly 1.35 to 1.82 short tons depending on classification. Avoid flat conversion factors — a supplier quoting "1.4 tons per yard" can be off by 25% at either end of the range. The calculator locks each product to its own density; wet material runs 5–15% heavier than these dry-basis figures.
| Material | Tons / cu yd | lb / cu ft | Typical $ / yd | Best for |
|---|---|---|---|---|
| Fill Dirt — Mixed / Unscreened | 1.55 | 115 | $5–$15 | Cheapest bulk fill; may contain small rocks or clods |
| Fill Dirt — Screened | 1.50 | 111 | $12–$25 | Rocks & roots removed; smoother final grade |
| Sandy Fill / Granular | 1.45 | 107 | $15–$30 | Best drainage; common under slabs and pavers |
| Sandy Loam Fill | 1.62 | 120 | $15–$25 | General-purpose fill; moderate compaction |
| Silty Fill | 1.55 | 115 | $10–$20 | Moisture-sensitive; verify drainage before use |
| Clay-Heavy Fill | 1.72 | 127 | $10–$20 | Compacts hard; shrinks 20–25% from loose volume |
| Structural / Engineered Fill | 1.65 | 122 | $15–$35 | Spec graded material for load-bearing placement |
| Topsoil — Unscreened | 1.35 | 100 | $10–$20 | Planting layer; never use as structural fill |
| Topsoil — Screened | 1.30 | 96 | $20–$40 | Premium lawn & bed layer; rocks and clods removed |
| Compost / Garden Mix | 1.00 | 74 | $25–$50 | Light organic blend for beds — not for grade-up |
| Fill Sand | 1.35 | 100 | $15–$35 | Drainage layers, pipe bedding, under-slab base |
Fill Dirt vs. Topsoil
Fill dirt is subsoil with minimal organic matter — it compacts to a stable, load-bearing surface for grade-up and backfill. Topsoil is the nutrient-rich upper layer (2–10% organic matter) for planting. They are not interchangeable: fill dirt will not grow plants, and topsoil decomposes and settles under structural loads. Many projects layer both — fill to build grade, then 4–6 inches of topsoil on top.
Bags vs. Bulk
A cubic yard equals 36 bags of 0.75 cu ft or 27 bags of 1 cu ft. Bagged material runs 5–10× the per-yard price of bulk, so bags make sense up to about 1–2 cubic yards; past that, a single bulk delivery almost always wins on price and effort. The bag equivalent in the results panel uses your selected retail bag size.
Buying guide
Screened, Unscreened, Clean & Structural Fill
Every supplier asks the same question first: screened or unscreened? The answer decides how the material handles, what it costs, and which layer of the job it belongs in. Grades below are the ones you will actually be quoted in the US.
| Grade | What it is | Typical $ / yd | Where it belongs |
|---|---|---|---|
| Unscreened / clean fill | Straight from a dig site, no processing. May contain small rocks, clods, and roots. | $5–$15 | Bottom 80% of a deep lift, rough grade, bulk volume nobody will plant in |
| Screened fill | Run through a 1/2–3/4 inch mesh; rocks and roots removed, uniform texture. | $12–$25 | Top 6 inches, under sod, final grade, anywhere that has to rake cleanly |
| Structural / select fill | Spec-graded material placed and tested to a target density, often 95% Standard Proctor. | $15–$35 | Under slabs, behind retaining walls, engineered pads, road base |
| Sandy fill / granular | Free-draining granular soil with minimal fines and almost no organic matter. | $15–$30 | Under pavers and slabs, wet or poorly drained sites, pipe bedding |
| Clay-heavy fill | High-plasticity subsoil that compacts hard and holds water. | $10–$20 | Pond liners, water-retention berms — not beneath structures or planting |
| Screened topsoil | Nutrient-rich upper layer with 2–10% organic matter, screened for planting. | $20–$40 | Lawns, garden beds, planting pockets — always the top layer, never structural |
| Compost / garden mix | Blended organic amendment, light and nutrient-dense, decomposes over time. | $25–$50 | Bed preparation and soil improvement, not grade-up or fill |
Screened vs. unscreened
- Unscreened runs about half the price per yard and is fine as bulk volume — just expect rocks, roots, and clods in the pile.
- Screened costs more but spreads, rakes, and grades without picking. It is the right call for the visible top layer.
- Layering both — unscreened below, screened on top — is how most crews get a clean finish without paying screened prices for the full depth.
What “clean fill” actually means
Clean fill refers to what is not in the dirt: no construction debris, trash, concrete chunks, glass, metal, stumps, or large roots. It says nothing about screening — clean fill can still contain small rocks and clods. Ask for a sample or the pit source before accepting a load, because organic debris rots and leaves voids that show up as sinkholes a year later.
Price per truckload: multiply the per-yard price by the load size to compare yards fairly. At $12/yd, a 14 yd³ tandem load is about $168 of material; at $25/yd it is $350. Freight of $50–$150 per load is billed on top either way, so two half loads almost always cost more than one full load.
Coverage & depth
How Far Does a Cubic Yard Go?
One cubic yard covers 324 square feet at 1 inch deep. Divide 324 by your depth in inches for any other depth — the chart below covers the common ones.
| Depth | Coverage per cu yd | Yards per 1,000 sq ft |
|---|---|---|
| 1" | 324 sq ft | 3.1 yd³ |
| 2" | 162 sq ft | 6.2 yd³ |
| 3" | 108 sq ft | 9.3 yd³ |
| 4" | 81 sq ft | 12.3 yd³ |
| 6" | 54 sq ft | 18.5 yd³ |
| 8" | 40.5 sq ft | 24.7 yd³ |
| 12" | 27 sq ft | 37.0 yd³ |
| Project type | Typical depth | Compaction? |
|---|---|---|
| Yard leveling | 3–6" | Light tamp OK |
| Foundation grade-up | 6–12" | Yes — 4 in lifts |
| Garden bed base | 4–8" | No — topsoil on top |
| Raised beds (filled) | 8–12" | No |
| Driveway subbase | 6–12" | Yes — multiple lifts |
| Under concrete slab | 4–6" | Yes — well compacted |
| Trench backfill | Full depth | Yes — 8 in lifts |
| Retaining wall backfill | Varies | Yes — spec density |
Foundation grading tip: build positive drainage away from the building — slope at least 6 inches over the first 10 feet from the foundation wall. Compact fill in 4-inch lifts, and avoid placing expansive clay directly against masonry. For significant low spots, add fill in lifts and compact each layer rather than dumping the full depth at once.
Depth reference
How Deep Should Fill or Topsoil Be?
Depth moves the order far more than area does — doubling the depth doubles the yardage. These are the finished depths contractors typically specify, measured after spreading and settling.
| Application | Typical finished depth | Notes |
|---|---|---|
| Overseeding / grass-seed topdressing | 1/4 – 1/2" | Just enough to cover seed and hold moisture |
| Topdressing an established lawn | 1/2" | Deeper smothers the existing turf — split into two passes |
| Regrading / settling repair | 2 – 4" | Feather edges so water still drains away from the house |
| Sod bed preparation | 3 – 4" | Firm, level, and free of rocks before rolls go down |
| New lawn over prepared subgrade | 4 – 6" | Root zone depth for a durable lawn |
| Flower bed / shrub bed | 6 – 8" | Annuals shallower, perennials and shrubs toward the deep end |
| Vegetable / raised garden bed | 10 – 12" | Root crops need the full 12 in; 18 in for deep raised beds |
| Foundation grade-up | 6 – 12" | Place in 4 in lifts, compacted, with positive drainage away |
| Driveway subbase | 6 – 12" | Multiple compacted lifts; deeper for heavier vehicle loads |
| Under a concrete slab | 4 – 6" | Well compacted and uniform — never on soft or organic soil |
Topsoil
6–12 in for gardens and lawns
Root depth decides the number. Root vegetables want 12 in or more.
Fill dirt
As deep as the grade requires
Build in 4–6 in lifts rather than dumping the full depth at once.
Compost
2–4 in, mixed in
Blend into the top 6–8 in instead of layering, to avoid a perched water table.
Uneven ground: measure the deepest point and the shallowest point in each area, average them, and enter that figure. For a yard that slopes from 2 in at the high side to 10 in at the low side, plan on 6 in — the calculator's slope mode handles a straight wedge with the same math automatically.
Conversions
Dirt Calculator Tons, Cubic Yards & Acres
Three constants do all the work: 27 cubic feet in a cubic yard, 43,560 square feet in an acre, and material density in tons per cubic yard. The tables below cover the conversions suppliers ask about most.
Yards ↔ tons
Loose delivered density, dry basis
| Material | Tons / yd³ | yd³ per ton | 10 tons ≈ |
|---|---|---|---|
| Fill dirt | 1.15–1.35 | 0.80 | 8 yd³ |
| Select fill | 1.20–1.40 | 0.77 | 7.7 yd³ |
| Topsoil | 1.00–1.20 | 0.90 | 9 yd³ |
| Sand | 1.30–1.50 | 0.71 | 7.1 yd³ |
| Crushed base | 1.35–1.55 | 0.69 | 6.9 yd³ |
Moisture adds 5–15% to these figures. If you are paying by the ton, ask whether the scale is certified and when the material was last watered.
Dirt Calculator Square Feet: Cubic Yards per 1,000 Sq Ft
Before compaction buffer
| Depth | Cubic yards | Cubic feet |
|---|---|---|
| 1" | 3.1 yd³ | 83 cu ft |
| 2" | 6.2 yd³ | 167 cu ft |
| 3" | 9.3 yd³ | 250 cu ft |
| 4" | 12.3 yd³ | 333 cu ft |
| 6" | 18.5 yd³ | 500 cu ft |
| 12" | 37.0 yd³ | 1,000 cu ft |
Multiply by your actual square footage ÷ 1,000, then add the buffer. A 2,500 sq ft lawn at 4 in ≈ 2.5 × 12.3 = 30.8 yd³ before overage.
Acres to cubic yards
Truckloads shown at 14 cu yd per tandem load, rounded up
| Acres | Depth | Cubic yards | Tandem loads |
|---|---|---|---|
| 1 acre | 6" | 807 | 58 |
| 1 acre | 12" | 1,613 | 116 |
| 5 acres | 12" | 8,067 | 577 |
| 5 acres | 24" | 16,133 | 1,153 |
| 10 acres | 24" | 32,267 | 2,305 |
One acre at a foot of fill is over 100 tandem loads — acreage grading is a supplier-quoted, machine-placed job, not a wheelbarrow project.
Budgeting
Fill Dirt Cost & Delivery Guide
Fill dirt costs roughly $15 to $55 per cubic yard delivered in most US markets, with unscreened bulk fill at the low end ($5–$15 material only) and screened fill at the top. Delivery typically adds $50–$150 per truckload within a 15-mile radius — freight, not material, is usually the biggest line item.
What Drives the Price You Pay
- Travel distance — dirt is heavy and freight dominates cost. Suppliers within 5 miles often quote a flat trip fee.
- Screened vs. unscreened — screening removes rocks and roots, and roughly doubles the per-yard price.
- Season — spring grading season pushes prices up 10–25%; late summer and fall are often cheaper.
- Quantity — orders under 5 cu yd may carry a short-load fee; orders over 20 cu yd often negotiate down per yard.
- Region — enter your ZIP above for a regional freight estimate; dense supplier networks in the Northeast and South trend cheaper than Mountain West or Pacific freight. Suppliers usually quote freight one of three ways — flat per truckload, per cubic yard, or per ton — so pick the mode your yard uses; per-yard and per-ton modes price small orders more fairly than a full truck minimum.
How Many Truckloads?
A standard single-axle dump truck holds about 10 cubic yards. Divide your buffered cubic yards by the truck capacity and round up — suppliers don't deliver fractional loads. Example: a 40 × 20 ft backyard at 6 in deep needs 17.0 cu yd with buffer → 17.0 ÷ 10 = 1.7 → 2 truckloads. Tandem (14 yd³) and tri-axle (16 yd³) trucks cut load counts on bigger jobs, and a pickup bed (~2.5 yd³) works for DIY hauling of small orders.
Delivery day
Truck Access, Minimums & Drop-Zone Prep
The order is only half the job — the truck has to reach the drop point and leave without tearing up the yard. Confirm access and fees when you book, not when the driver is already at the curb.
Site access checklist
- A path at least 12 ft wide with 13–14 ft of overhead clearance for tandem and tri-axle trucks
- Firm ground — no soft lawns, fresh fill, or saturated soil that a loaded truck will sink into
- No grades steeper than about 10% on the approach or the dump spot
- Overhead wires, tree limbs, and gate heights checked before the driver arrives
- No irrigation heads, septic lids, or unmarked utilities inside the drop zone
- The drop spot marked with cones, flags, or a person guiding the driver
Hidden delivery charges
- Minimum haul fee — Trucking companies lose money on tiny loads — 2 yards often carries the same trip fee as 10. Order in bulk where the site allows.
- Short-load surcharge — Many yards apply a fee below 5 cu yd. Ask what the threshold is before you split an order.
- Tailgating — Spreading while the truck creeps forward saves hours of shoveling. Ask if the driver can tailgate; not every yard offers it.
- Wet weight — If you pay by the ton, rain the day before is billed as water. Schedule after a dry stretch and ask about a scale ticket.
Three questions to ask when booking: Is freight a flat trip fee, per cubic yard, or per ton? How far can the driver back in? And what is the policy if the load weighs heavier than quoted?
Drop-zone options
| Method | Best when | Watch out for |
|---|---|---|
| Single pile | The spread area is close to the drop point and you have a machine or crew to move it | A 10 yd³ pile is a serious obstruction — pick a spot you can work around |
| Tailgate spread | Driveway subbase, long lanes, or a strip you want dumped in a windrow | Needs a clear drive path and a driver willing to creep while spreading |
| Multiple small piles | Several garden beds or zones far apart | Usually billed as extra stops or a second delivery |
| Bagged pallets | Small beds, tight access, or no machine available | 5–10× the per-yard cost — practical only up to about 1–2 yd³ |
Moving it
How Much Work Is a Yard of Dirt?
Calculating the volume is the easy part; moving it is where the job gets long. A contractor wheelbarrow holds about 3 cubic feet, so one cubic yard is roughly 9–10 loads — and that number climbs fast with volume.
| Volume | Wheelbarrow loads | Hand labor | What it really takes |
|---|---|---|---|
| 1 cu yd | ≈ 10 | 1–2 hours | Shovel, rake, and a tamper |
| 5 cu yd | ≈ 50 | A full day, exhausting | Rent a mini skid steer or stand-on dumper |
| 10 cu yd | ≈ 100 | Multiple days by hand | Skid steer or compact track loader is the practical minimum |
| 20 cu yd | ≈ 200 | Several days with a machine | Skid steer plus operator, or a tracked loader with a larger bucket |
| 40+ cu yd | 400+ | Not a DIY volume | Excavator or dozer with grading oversight; plan phasing and drainage |
Spreading labor
$30–$60 / hr
Typical crew rate for hand spreading, raking, and compacting small to mid-size fills.
Machine rental
$150–$400 / day
Skid steer or mini loader, before delivery, fuel, and operator. Worth it above ~5 cu yd.
Wheelbarrow reality
≈ 3 cu ft per load
A 27 cu ft yard is 9–10 trips — measure the distance before deciding to go manual.
Compaction is not optional on structural fill. Spread in 4–6 inch lifts and compact each lift before the next one goes down. Compacting one thick layer from the top leaves the bottom loose, and that is what settles under a slab or driveway a year later.
Answers
Frequently Asked Questions
Multiply length × width × depth with all measurements in feet, then divide by 27 to get cubic yards. For a 20 × 15 ft area at 6 inches deep: 20 × 15 × 0.5 ÷ 27 = 5.56 cubic yards of base volume. Add a compaction buffer — 15% is the reliable default — and order about 6.4 cubic yards.
When the Formula Is Not Enough
The L × W × D ÷ 27 method covers residential leveling and routine grading. Call a geotechnical engineer before ordering fill for retaining walls over 4 ft, building foundations, loads over ~100 cubic yards, high-plasticity clay subsoils, or any regulated site — many municipalities require an engineered grading plan above 50 cu yd or 4 ft of fill height.