Material Calculator

How this calculator works

Enter the length and width of the area in feet, the depth or thickness in inches, then pick your material. The calculator returns volume in cubic yards, cubic feet and cubic metres, an estimated weight in tons, the number of bags if it is sold bagged, and a cost estimate you can adjust to your local price.

Each material carries its own bulk density, waste allowance and typical application depth, so switching materials changes the answer — a 4-inch concrete slab and a 3-inch mulch bed of the same footprint need very different volumes.

Why depth is the biggest source of error

Going from 3 inches to 4 inches over a 20 × 20 ft area is an extra 2.5 cubic yards. On ready-mix concrete that is roughly a $400 difference. Measure the actual form depth rather than assuming it, and add a waste allowance for uneven subgrade.

Ordering rules of thumb

• Ready-mix concrete is sold by the cubic yard with a minimum order and a short-load fee below about 3 yards.
• Bagged concrete only makes sense below roughly 1 cubic yard (about 45 × 80 lb bags); above that, ready-mix is cheaper and far less work.
• Mulch, topsoil, sand and gravel are sold by the cubic yard in bulk or by the bag at garden centres — both are shown.
• Sod is sold by the square foot or by the pallet, and pallet coverage varies by grower.

The formula is identical for eight of the nine materials

Eight materials here sell by volume and price by the cubic yard: concrete, gravel, mulch, topsoil, sand, paver base, river rock and fill dirt. The ninth, sod, sells by the square foot.

The arithmetic never changes. Area in square feet × depth in feet, plus the waste allowance, ÷ 27. Depth comes off a tape in inches, so divide by 12 first.

Gravel, worked through: 12 × 12 ft is 144 sq ft; at 4 inches that is 0.333 ft, so 144 × 0.333 = 48 cubic feet in place. Gravel's default waste is 10%, taking the order to 52.8 cubic feet, and 52.8 ÷ 27 = 1.96 cubic yards. At 105 lb per cubic foot that weighs 5,544 lb — 2.77 tons — and at $52 per yard it costs about $102 before delivery.

Prices here are US national averages, not quotes, which is why the price field on the page is editable — put your supplier's number in before you believe a total.

A cubic yard weighs whatever the material weighs

Mulch is the lightest of the nine at 25 lb per cubic foot, so a yard is 675 lb. Fill dirt at 95 makes that yard 2,565 lb; concrete at 150 makes it 4,050 lb.

Across the eight bulk materials the spread runs from 25 to 105 lb per cubic foot — a little over four times, six times with concrete counted. That decides how the order arrives: a tandem dump truck that hauls 12 cubic yards of crushed stone is weight-limited at about 17 tons; filled with mulch, it runs out of bed space at under a third of that.

Topsoil and river rock both sit at 90 lb per cubic foot, so a yard of each weighs 2,430 lb. One costs $35 a yard at the national average, the other $105 — you are paying for screening, washing and grading by size, not for mass.

Load-bearing and drainage want opposite stone

"Gravel" is not one product. Base stone — ¾-inch minus, road base, paver base — is crushed with the fine dust left in, and the fines are the point: watered and compacted in 2-inch lifts, they bind it into a semi-locked layer that spreads a wheel load. Clean stone is screened to one size with the fines washed out; it never locks up, which a drain needs and pavers cannot tolerate.

Swap them and the failure is specific. Clean stone under pavers stays loose and they rock within a season — what the paver base calculator is built around. Base stone with fines around a drain migrates into the pipe until water stops moving, the line the gravel calculator draws.

River rock is a third thing: rounded, graded by size, decorative only, and large grades need roughly 20% more volume than pea gravel at the same depth. Drainage wants clean and uniform, structure wants graded and compacted, and no single stone does both.

Soil, fill and mulch are three products in one aisle

Topsoil is screened loam with organic matter in it — the layer that grows things, which is why the topsoil calculator quotes screened and unscreened separately. Fill dirt is unscreened subsoil: 30–40% cheaper per yard, structurally useful, nutritionally useless. Nothing grows in it well until it is capped with 4–6 inches of topsoil — the job the fill dirt calculator sizes. Order the cheap one for a bed and you buy the loam on top anyway; order the expensive one to raise a pad and you waste it.

Both settle, and that is not spillage. Topsoil loses 15–25% after watering, so a 6-inch loose layer finishes near 4½ inches; dumped fill loses 20% or more in its first year. The waste field is where that belongs.

Mulch is not soil at all. It goes on at 2–3 inches rather than 6, and past 3 inches it holds moisture against trunks and starves roots — the cone piled around a tree is the most common way one gets killed. The mulch calculator treats 3 inches as a ceiling.

One pit, nine materials, nine totals

Fix the job: a 12 × 12 ft pit, 4 inches deep — 48 cubic feet in place, 52.8 cubic feet with 10% waste, 1.96 cubic yards. Now change only the material.

National averages, material only, delivery excluded.

Nothing lines up. Fill dirt is the cheapest thing you can drop in the hole at $43 and river rock the dearest at $205 — a fivefold spread, five pounds per cubic foot apart. Gravel and paver base weigh the same and sit $8 apart, and are still not interchangeable, because only one compacts. Pick the material on the job it has to do; density then decides what it costs to get there.

Sod sells by area, so cubic yards never apply: 144 sq ft with 5–10% over is 158 sq ft, and its own 1-inch thickness is where the 0.33-ton figure comes from. Waste defaults on the page are 5% for concrete, mulch and sod against 10% for the rest, so those rows land slightly low when you run them live.

Bags, bulk, and the truck that cannot reach the backyard

Format follows volume, and bagging multiplies the price per yard by two to six. Bagged mulch is 2 cubic feet at $3.95 — 13.5 bags to the yard, $53 against $38 in bulk. Bagged topsoil is 1 cubic foot at $3.25, or $87.75 a yard against $35. Gravel in 50 lb bags runs near $243 a yard. Bags win in two situations: you need less than about a yard, or no truck can reach the spot.

Bulk is priced by the trip as much as the yard: delivery, a minimum order and a short-load charge sit on top of the per-yard number, and coming back for two yards you were short costs more than the extra half yard would have. A loaded dump truck also needs a firm approach and clear overhead for the bed; if it cannot get in, the material lands at the kerb.

Concrete and sod are sold on a schedule, not a volume

Concrete is quoted by the cubic yard like the aggregates, but you are hiring a truck as much as buying material: water and cement go in at the plant and the clock starts when the drum fills. Plants charge a minimum, often a full yard, plus a short-load fee below about 3 yards, so a half-yard pour can cost nearly what a 3-yard pour does. Above roughly a yard, ready-mix at $165 a yard beats bagged mix at $308; below half a yard it loses. The concrete calculator holds waste at 5% because a slab is monolithic — you cannot stop halfway and start again.

Sod sells by the square foot, the roll, or the 450–500 sq ft pallet, and its constraint is time: laid within 24 hours, watered the same day, edges that never match your measurements. Order 5% over on a rectangle and 10% on anything curved, over 4–6 inches of amended topsoil that is a separate order. The sod calculator returns area, pallets and cost, and stops there.

The other seven are an ordinary purchase: carried home, spread at your own pace, topped up next weekend. These two are scheduled events, and both punish an underestimate more than an overestimate.