Geometry
Material Calculator
Cubic yards, tons, and bag counts for concrete, gravel, mulch, topsoil, and sand.
Result
Enter your numbers and press Calculate to see the result.
Calculating…
How much material do you need?
Every bulk material follows the same three steps: work out the area, multiply by the depth to get a volume, then convert that volume into whatever unit the supplier sells in.
cubic yards = length (ft) × width (ft) × depth (in) ÷ 12 ÷ 27
The two constants are the ones people forget. Depth is almost always given in inches while length and width are in feet, so it has to be divided by 12 first. And there are 27 cubic feet in a cubic yard, not 3 — a yard is three feet in each of three dimensions.
Concrete: how many bags per cubic yard
Bagged concrete is sold by weight, and each bag yields a fixed volume of mixed concrete:
| Bag size | Yield | Bags per cubic yard | Bags per cubic foot |
|---|---|---|---|
| 40 lb | 0.30 cu ft | 90 | 3.3 |
| 50 lb | 0.375 cu ft | 72 | 2.7 |
| 60 lb | 0.45 cu ft | 60 | 2.2 |
| 80 lb | 0.60 cu ft | 45 | 1.7 |
The crossover point is worth knowing before you load a trolley. At roughly one cubic yard — 45 bags of 80 lb, about 3,600 lb of material — ready-mix delivery is usually cheaper and always less work. Below about half a yard, bags win.
Worked example: a 10 × 10 patio slab
| Step | Working | Result |
|---|---|---|
| Area | 10 ft × 10 ft | 100 sq ft |
| Depth | 4 in ÷ 12 | 0.333 ft |
| Volume | 100 × 0.333 | 33.3 cu ft |
| Cubic yards | 33.3 ÷ 27 | 1.23 yd³ |
| With 10% waste | 1.23 × 1.10 | 1.36 yd³ |
| 80 lb bags | 36.7 cu ft ÷ 0.60 | 62 bags |
That is already past the ready-mix crossover. Ordering 1.5 yards delivered beats carrying 62 bags.
Converting cubic yards to tons
Suppliers quote gravel, sand, and topsoil by the ton as often as by the yard, and the conversion needs the material's density — there is no universal factor:
| Material | lb per cubic yard | Tons per cubic yard | Cubic yards per ton |
|---|---|---|---|
| Concrete | 4,050 | 2.03 | 0.49 |
| Asphalt | 4,000 | 2.00 | 0.50 |
| Gravel / crushed stone | 2,800 | 1.40 | 0.71 |
| River rock | 2,700 | 1.35 | 0.74 |
| Sand | 2,700 | 1.35 | 0.74 |
| Topsoil | 2,000 | 1.00 | 1.00 |
| Wood mulch | 800 | 0.40 | 2.50 |
| Bark / wood chips | 700 | 0.35 | 2.86 |
The spread is enormous — a cubic yard of concrete weighs five times what a cubic yard of mulch does. These are dry loose values; wet material can weigh 10–20% more, which matters when a delivery is priced by weight and when you are checking a trailer's load rating.
Mulch, bark, and pine straw coverage
Mulch is sold in 2 cubic foot bags, which gives 13.5 bags per cubic yard. A standard pallet holds about 65 bags, or roughly 4.8 cubic yards.
| Depth | Coverage per cubic yard | Coverage per 2 cu ft bag |
|---|---|---|
| 1 inch | 324 sq ft | 24 sq ft |
| 2 inches | 162 sq ft | 12 sq ft |
| 3 inches | 108 sq ft | 8 sq ft |
| 4 inches | 81 sq ft | 6 sq ft |
Two to three inches is the usual recommendation — enough to suppress weeds and hold moisture, without smothering roots. A bale of pine straw covers roughly 35–50 sq ft at that depth, so it is priced per bale rather than by volume.
Depth by project
| Project | Typical depth |
|---|---|
| Mulch beds | 2–3 in |
| Gravel path or walkway | 2–3 in |
| Gravel driveway | 4–6 in, often in two layers |
| Concrete patio or sidewalk | 4 in |
| Concrete driveway | 4–6 in |
| Topsoil for new lawn | 4–6 in |
| Paver base | 4–6 in of compacted gravel |
Why the waste allowance matters
Order the exact calculated figure and you will come up short. Ground is never perfectly level, sub-base settles, material compacts, and some is always lost in handling. Add 5–10% — the higher end for concrete, where running out mid-pour means a cold joint and a visible seam that cannot be fixed afterwards.
Being over on bulk material is cheap. Being under on a concrete pour is not.
For the plain geometry, the area calculator handles irregular shapes and the volume calculator covers cylinders and spheres. To convert between length units first, use the length converter.
Material Calculator — frequently asked questions
How many 80 lb bags of concrete are in a cubic yard?
45. An 80 lb bag yields 0.60 cubic feet and there are 27 cubic feet in a cubic yard. A 60 lb bag yields 0.45 cu ft, so it takes 60 of those.
How do I calculate cubic yards?
Multiply length by width in feet, multiply by the depth in feet, then divide by 27. If the depth is in inches, divide it by 12 first.
How many cubic feet are in a cubic yard?
27, not 3. A yard is three feet in each of three dimensions, so 3 x 3 x 3 gives 27 cubic feet.
How many tons is a cubic yard of gravel?
About 1.4 tons, at roughly 2,800 lb per cubic yard. Topsoil is around 1 ton and concrete about 2 tons, so the conversion depends entirely on the material.
How many bags of mulch are in a cubic yard?
13.5 bags at the standard 2 cubic foot size. A pallet holds about 65 bags, which is roughly 4.8 cubic yards.
How much mulch do I need?
At the usual 2 to 3 inch depth, one cubic yard covers 162 sq ft at 2 inches or 108 sq ft at 3 inches. A single 2 cu ft bag covers about 12 sq ft at 2 inches.
When is ready-mix cheaper than bags?
At around one cubic yard. That is 45 bags of 80 lb concrete, about 3,600 lb to carry and mix, and delivery is usually cheaper as well as far less work.