construction
Cubic Yards, Tons, and Density: Ordering Gravel, Soil, and Mulch
Area × depth in inches ÷ 12 ÷ 27 gives cubic yards; density turns yards into tons. The real numbers for gravel, soil, mulch, asphalt, concrete bags, and sod.
Most bulk-material orders go wrong before anyone looks at a price. Someone measures a 12 × 40 ft driveway, decides on 4 inches of stone, and then multiplies feet by inches, or divides by 9 when it should be 27, or asks for “six yards” from a quarry that sells by the ton. Almost every bulk order comes down to one conversion, cubic feet ÷ 27 = cubic yards, and one lookup, density, which turns yards into the tons a quarry weighs on its scale. Get those two steps right and the rest is allowances.
This post goes through both, with every worked number produced by the libraries behind our construction calculators, and then covers the product-specific details: compaction, waste, concrete bag yields, asphalt, and sod.
The formula, and the two ways people break it
A cubic yard is a cube 3 feet on each side, so it holds 3 × 3 × 3 = 27 cubic feet. You measure area in square feet and depth in inches, which gives:
cubic yards = area (sq ft) × depth (in) ÷ 12 ÷ 27The ÷ 12 converts inches to feet and the ÷ 27 converts cubic feet to cubic yards. That’s exactly what our shared volumeCuft and cuftToCuyd helpers do, and every landscape calculator on the site uses them.
Take that 12 × 40 ft driveway (480 sq ft) at 4 inches deep:
| Step | Math | Result |
|---|---|---|
| Correct | 480 × 4 ÷ 12 ÷ 27 | 5.93 yd³ (160 ft³) |
| Forgot ÷ 12 | 480 × 4 ÷ 27 | 71.1 yd³ (12× too much) |
| Divided by 9 | 160 ÷ 9 | 17.8 yd³ (3× too much) |
The ÷ 9 mistake comes from mixing up square yards (9 sq ft) with cubic yards (27 cu ft). Paving crews really do use square yards, as the asphalt section below shows, which is part of why the mix-up keeps happening.
Depth has a big effect. Since 1 yd³ is 27 ft³, and 1 inch over 1 sq ft is 1/12 ft³, one cubic yard spread 1 inch deep covers 27 × 12 = 324 sq ft. Divide by the depth to get coverage at any thickness:
| Depth | Coverage of 1 yd³ |
|---|---|
| 1 in | 324 sq ft |
| 2 in | 162 sq ft |
| 3 in | 108 sq ft |
| 4 in | 81 sq ft |
That’s why a “yard” of mulch covers 108 sq ft at the usual 3 inches, a smaller bed than most people picture. Our mulch calculator computes this with coveragePerCuyd(depth) = 324 ÷ depth.
Why suppliers want tons: density
Quarries and many landscape yards sell stone by weight because the truck is weighed on a scale. To convert, you need the material’s bulk density in pounds per cubic yard:
US tons = cubic yards × lb per yd³ ÷ 2,000A short ton is 2,000 lb. A metric tonne is 1,000 kg ≈ 2,204.6 lb, so the same load is about 9% fewer tonnes than US tons. If a supplier quotes in tonnes, check which one they mean. The unit converter handles lb ↔ t directly.
Bulk density changes a lot with the material, and for any single material it varies with rock type, grading, and moisture. Here’s what we could confirm from published sources, next to the presets our calculators ship with:
| Material | Published figure | Our preset | Tons per yd³ (preset) |
|---|---|---|---|
| Crushed stone (#57) | Sand/gravel/rock 2,500–2,900 lb/yd³ (North Bay Materials); gravel, dry 105 lb/ft³ = 2,835 lb/yd³ (Engineering ToolBox) | 2,800 | 1.40 |
| Pea gravel | same range | 2,700 | 1.35 |
| Road base / crusher run | same range | 2,900 | 1.45 |
| River rock | same range | 2,600 | 1.30 |
| Sand | same range; sand, dry 97 lb/ft³ = 2,619 lb/yd³ (Engineering ToolBox) | 2,700 | 1.35 |
| Topsoil, dry | dirt, loose dry 76 lb/ft³ = 2,052 lb/yd³ (Engineering ToolBox); “Dirt” 2,200–2,500 (North Bay) | 2,100 | 1.05 |
| Topsoil, wet | gravel and sand gain 20–22 lb/ft³ wet vs dry (Engineering ToolBox) | 2,700 | 1.35 |
| Garden soil / compost | ”Soil, Compost, Conditioner” 1,000–1,500 (North Bay) | 1,500 / 1,000 | 0.75 / 0.50 |
| Bark mulch, wood chips | 500–800 (North Bay) | 500–800 (weight hint only) | 0.25–0.40 |
| Hot-mix asphalt, compacted | ≈ 145 lb/ft³ (Iowa DOT HMA manual, ch. 2) = 3,915 lb/yd³ | 145 lb/ft³ | 1.96 |
Tons per yd³ is just the preset ÷ 2,000. The ft³ → yd³ conversions are × 27. Our presets sit inside the published ranges, and in every calculator the density field is editable. Before you order, ask your yard what their product weighs and enter that number.
Parcel carriers use density in reverse. The 139 divisor behind dimensional weight is really a floor of 1,728 ÷ 139 ≈ 12.4 lb/ft³, and any box lighter than that is billed as if it weighed that much; the 139 divisor, explained works through it.
The practical point is that one volume can be several different weights. Running our gravel calculator on the same 5.93 yd³, with its waste field set to 0, gives:
| Material | Tons for 480 sq ft × 4 in |
|---|---|
| River rock (2,600) | 7.70 |
| Pea gravel (2,700) | 8.00 |
| Crushed stone (2,800) | 8.30 |
| Road base (2,900), no compaction | 8.59 |
If you’re comparing a per-ton quote with a per-yard quote, convert one into the other before deciding which is cheaper. The gravel calculator prices by either one for this reason.
The same weight figure also tells you whether a trip in your own truck is realistic. Our topsoil calculator puts 1,000 sq ft of new lawn at 4 inches at 12.35 yd³, which is 12.96 tons dry at 2,100 lb/yd³ and 16.67 tons at the wet preset of 2,700. That’s a delivery job. Mulch goes the other way: 400 sq ft at 3 inches is 3.70 yd³ but only about 1,850–2,960 lb.
Compaction: the allowance that doesn’t show up in the area math
Clean, washed stone like #57 crushed stone, pea gravel, and river rock barely consolidates. Graded road base and crusher run, which contain fines that fill the gaps, lose volume when you run a plate compactor over them. If the finished base must be 4 inches thick after compaction, you have to spread more than 4 inches of loose material.
Our gravel calculator treats the compaction percentage as the volume the stone loses, and divides the finished volume by (1 − loss) to get the loose amount to order. The road-base preset sets it to 15%, and the other presets set it to 0. Our paver calculator defaults its base layer to 4 inches with the same 15% and the same math. For the 480 sq ft driveway at 4 inches compacted:
| Road base | Volume | Tons (2,900 lb/yd³) |
|---|---|---|
| No allowance | 5.93 yd³ | 8.59 |
| 15% compaction loss (÷ 0.85) | 6.97 yd³ | 10.11 |
The 10–20% compaction range is a trade rule of thumb. We couldn’t find a standard or agency source that pins it down, and the right figure depends on the gradation and how hard you compact, so ask your quarry. There’s also some arithmetic to watch. “Loses 15% of its volume” and “order 15% extra” aren’t quite the same thing. If loose material shrinks by 15%, you need finished ÷ 0.85, which is 17.6% extra, not 15%. A 20% loss means 25% extra. Both calculators do the division for you, so enter the loss your quarry quotes, not the extra.
Waste: small, but not zero
Waste covers spillage, an uneven subgrade, forms bowing outward, and the material left in the wheelbarrow. Our calculators use these defaults:
| Calculator | Default extra | Notes |
|---|---|---|
| Concrete | 10% | hint says 5–10% |
| Asphalt | 5% | applied to asphalt and base |
| Sod | 5% | chips for 5 / 8 / 10% for curves and cuts |
| Pavers | 5% | 10–15% for herringbone and curves (pattern presets) |
| Mulch, topsoil | 0% | editable; topsoil’s field covers settling (10–20% in the FAQ) |
| Gravel | 5% | separate from compaction; applied on top of the compaction-adjusted volume |
In the gravel calculator the two stack: 480 sq ft of road base at 4 inches with the 15% compaction loss and the 5% default waste comes to 7.32 yd³ (10.61 tons). One limitation is worth knowing. The gravel-base line in the asphalt calculator applies only your waste percentage, with no separate compaction allowance.
Concrete: bag yields and the one-yard line
Concrete is sold by volume, whether in bags or by the truckload. Quikrete’s Concrete Mix data sheet (No. 1101) lists the yields, and our CONCRETE_BAG_YIELD_CUFT table uses the same numbers:
| Bag | Yield (Quikrete 1101) | Bags per yd³ |
|---|---|---|
| 40 lb | 0.30 ft³ | 90 |
| 50 lb | 0.375 ft³ | 72 |
| 60 lb | 0.45 ft³ | 60 |
| 80 lb | 0.60 ft³ | 45 |
(The data sheet also lists a regional 90 lb bag at 0.675 ft³. Our calculator doesn’t offer that size.)
A 10 × 10 ft patio slab 4 inches thick is 33.33 ft³ (1.23 yd³). With the default 10% waste, our concrete calculator makes that 36.67 ft³, or 62 bags of 80 lb mix, which is 4,960 lb to lift and mix by hand. Once the total including waste reaches 1 yd³, the calculator suggests ready-mix or a rented mixer trailer. That threshold is our rule of thumb, not an industry standard. At 4 inches thick, 1 yd³ is only 81 sq ft of slab before waste, or about 74 sq ft with 10% waste, so a surprising number of backyard pads cross it.
Ready-mix plants set their own minimum loads and small-load fees, so the calculator has fields for both. It rounds the truck order up to the next quarter yard and compares that cost with the bag total.
Asphalt: 145 lb per cubic foot
For compacted hot-mix asphalt, the Iowa DOT’s HMA manual gives a density of “approximately 145 pounds per cubic foot,” and that’s the default in our asphalt calculator (you can edit it). Paving crews often think in square yards per inch instead: 145 × 9 ÷ 12 = 108.75 lb per square yard per inch.
At that density, one US ton of asphalt covers:
| Compacted thickness | Sq ft per ton |
|---|---|
| 2 in | 82.8 |
| 3 in | 55.2 |
| 4 in | 41.4 |
So a 1,000 sq ft driveway at 3 inches needs 250 ft³ × 145 ÷ 2,000 = 18.1 tons before waste. For our 480 sq ft example at 3 inches with a 6 inch base and the default 5%, the calculator returns 9.13 tons of asphalt plus 9.33 yd³ (13.07 tons) of base stone at 2,800 lb/yd³. The base weighs more than the asphalt because it’s twice as thick.
Sod: square feet, rolls, and pallets
Sod is the one material here you order by area, not volume, but it still has packaging units to round up to. According to Sod Solutions, slabs are 16 × 24 inches (about 2.66 sq ft) and are “sold as 400, 450, and 500 sq. ft. pallets”. Mini hand rolls are 40 × 18 inches (5 sq ft) on 400, 450, and 500 sq ft pallets. Large rolls are 60 × 24 or 80 × 18 inches (10 sq ft) and usually come on 500–700 sq ft pallets. No single standard exists, which is why every size in our sod calculator is editable.
With the defaults (10 sq ft rolls, 500 sq ft pallets at the low end of that range, 5% waste), a 1,200 sq ft lawn becomes 1,260 sq ft: 126 rolls, or 3 pallets delivering 1,500 sq ft. If your farm ships on a larger pallet, enter its real size. At 700 sq ft per pallet, the same lawn needs 2.
Before you order
- Measure in feet, depth in inches, and run area × depth ÷ 12 ÷ 27. For odd shapes, add sections: the landscape calculators accept rectangles, circles, triangles, and known areas, and they read inputs like
12' 6"or3.5m. - Ask the supplier two questions: do they sell by the ton or the yard, and what does their product weigh per yard? Enter that density instead of relying on our preset.
- Add compaction for road base (and round up), and waste for everything else.
- Compare quotes in the same unit. Every calculator shows both yards and tons. If you’re the one quoting the job, the construction estimate generator turns those quantities into a line-item PDF estimate.
For a trench, the French drain calculator uses the same yard-and-ton math, minus the volume the pipe takes up. A 50 ft trench 12 inches wide and 18 inches deep with a 4 inch pipe needs 2.62 yd³ of drainage stone after subtracting the pipe, or 2.75 yd³ (about 3.71 tons at 2,700 lb/yd³) with the calculator’s default 5% extra.
A block retaining wall needs the same math twice: crushed stone for the base trench, usually 6 inches compacted, and clean drainage gravel behind the blocks. The retaining wall calculator estimates both in yards and tons alongside the block count.
For surfaces rather than volumes, where you buy by the gallon, the roll, or the box, how much paint, wallpaper, and tile to buy does the same job for coverage and waste factors.
All of these calculators run entirely in your browser, and nothing you type is sent anywhere. Start with the one for your material: gravel, topsoil, mulch, concrete, asphalt, pavers, or sod.