How we calculate

Updated Sep 29, 2026

Every calculator on this site runs the same math, with different presets for the material, depth and typical price. Here is exactly what happens between the numbers you type and the numbers you see.

Area

For a rectangle, I multiply length by width.

Area = Length × Width

For a circle, I use the radius, which is half the diameter you enter:

Area = π × (Diameter ÷ 2)²

For a triangle:

Area = ½ × Base × Height

If your job isn’t a simple shape, or you already know the square footage, you can type the area directly instead of a length and width. You can also add more than one area to a single job, for an L-shaped bed or a driveway plus a path, and the amounts add together.

Depth

Depth is entered in inches, or centimeters in metric, and converted to feet by dividing by 12, since area is in square feet and the volume formula needs matching units.

Volume

Area in square feet times depth in feet gives cubic feet. Dividing by 27 gives cubic yards, because a cubic yard is a cube 3 feet on a side, and 3 times 3 times 3 is 27.

Cubic yards = (Area × Depth in feet) ÷ 27

For the metric figure, 1 cubic yard equals 0.764554858 cubic meters.

Extra for settling and waste

Loose material settles once it’s spread, and some is always lost to uneven ground, overfill or cutting pieces to fit. I add a percentage on top of the raw volume, from 0 to 15% depending on the material: gravel and rock usually need less, irregular jobs and base layers usually need more. You can change this yourself in the “Prices & extras” section on any tool page.

Weight

Weight comes from cubic yards times the material’s density, in tons per cubic yard. I show a typical figure plus a low-high range, since density changes with moisture, grading and how tightly the material has settled.

Tons = Cubic yards × Density (tons per cubic yard)

A US short ton is 2,000 pounds. Multiplying by 0.90718474 converts it to metric tonnes.

Bags

For material sold in bags, I divide the volume in cubic feet by the bag size and round up, since you can’t buy part of a bag. Metric bag counts assume 25 kg bags.

Bags = Volume (cu ft) ÷ Bag size (cu ft), rounded up

Order amounts

Suppliers sell bulk material by the half yard or half ton, so the order figures on each tool page round the raw cubic yard and ton numbers up to the next half unit.

Cost

For bulk material, I multiply the price per ton or per cubic yard (whichever basis you pick) by the amount, then add any delivery fee you enter. For bagged material, I multiply the bag price by the bag count. Whichever option comes out cheaper is flagged. Every price shown by default is a typical US estimate, meant to be replaced with a real quote from your own supplier.

Coverage

Some tools also work backward: given cubic yards on hand and a depth, I find the square footage that amount covers, by multiplying the cubic yards by 27 to get cubic feet, then dividing by the depth in feet.

Coverage (sq ft) = (Cubic yards × 27) ÷ Depth (feet)

How the numbers are checked

The calculation engine behind these tools has its own automated tests, built from cases worked out by hand before any of the code was written. As one check, a driveway job of 20 by 12 feet at 4 inches deep comes to 2.96 cubic yards on this site, matching the same input run through two other well-known online calculators. Every material’s density, every project’s suggested depth and every price on this site carries at least two independent sources, dated and listed below, and again on each tool’s own page.

Limits

These numbers assume flat ground at one even depth; a sloped or uneven site needs more material than a flat calculation predicts. Moisture changes weight a lot, especially for soil and mulch, so a real load can weigh more or less than the typical figure shown here. When you actually place an order, your supplier’s scale and their own minimum order size are the final word, not this page.

Density of every material

Material	Typical (tons/yd³)	Typical (t/m³)	Range	Extra	Bags
Pea gravel	1.4	1.66	1.3–1.5	10%	0.5 cu ft
#57 stone	1.4	1.66	1.3–1.5	10%	0.5 cu ft
Crusher run	1.5	1.78	1.25–1.8	10%	Bulk only
#411 stone	1.5	1.78	1.35–2	15%	Bulk only
River gravel	1.45	1.72	1.3–1.6	10%	0.5 cu ft
Decomposed granite	1.4	1.66	1.25–1.5	15%	0.5 cu ft
River rock	1.35	1.6	1.2–1.75	10%	0.5 cu ft
Landscape rock	1.35	1.6	1.2–1.5	10%	0.5 cu ft
Crushed stone	1.45	1.72	1.3–1.7	10%	0.5 cu ft
Lava rock	0.65	0.77	0.5–0.8	5%	0.5 cu ft
Marble chips	1.3	1.54	1.2–1.5	5%	0.5 cu ft
Topsoil	1.1	1.31	0.9–1.4	10%	0.75, 1, 1.5 cu ft
Fill dirt	1.2	1.42	1–1.5	15%	Bulk only
Garden soil mix	0.65	0.77	0.5–0.85	10%	0.75, 1, 1.5 cu ft
Sand	1.3	1.54	1.1–1.5	5%	0.5 cu ft
Limestone	1.4	1.66	1.2–1.6	10%	0.5 cu ft
Asphalt millings	1.45	1.72	1.2–1.6	10%	Bulk only
Concrete	1.95	2.31	1.85–2.05	10%	0.6 cu ft
Bark mulch	0.3	0.36	0.2–0.4	5%	2 cu ft