Gravel Calculator

What this sheet does that the ranking gravel calculators do not

Not one of the seven pages that rank for gravel calculator cites a source for the density it converts yards into tons with, the only number in the calculation that is not arithmetic. Everything below was missing from all seven:

• A density with its source printed next to it. Type your supplier’s number in and theirs wins, on the takeoff too.
• Materials we could not source have no default at all, not a number we made up.
• Compacted to loose, with a published factor instead of an arbitrary “add 10 percent.”
• Up to four areas of three shapes, added together, priced two ways and costed against a truck capacity you control.
• Short tons and metric tonnes side by side, about 10 percent apart.
• A dimensioned plan and section, plus a takeoff you can export as CSV or print.

How to calculate gravel, stone or rock

1. Get the area in square feet. Length times width for a rectangle, pi times the diameter squared divided by four for a circle, base times height divided by two for a triangle.
2. Convert the depth to feet. Inches divided by 12: 4 inches is 0.3333 ft.
3. Multiply and divide by 27. Area times depth is cubic feet; 27 cubic feet make a cubic yard.
4. Convert to tons with a density you can defend. Cubic yards times pounds per cubic yard, divided by 2,000.

Area           A  =  L x W        rectangle
                  =  pi x D^2 / 4  circle
                  =  B x H / 2     triangle
In-place vol   Vp =  sum( A x Depth )        (feet)
Loose volume   Vl =  Vp / LF                 (LF = load factor)
Cubic yards    Y  =  Vl / 27
Order          Yo =  ceil( Y / 0.5 ) x 0.5
Weight         W  =  Y x density(lb per cu yd)
Short tons     T  =  W / 2000
Metric tonnes  t  =  W / 2204.62
Loads          N  =  ceil( Yo / truck capacity )

One cubic yard covers 81 square feet at 4 inches, pure geometry whatever the material is. But one short ton of dry 1/4-2 in gravel is about 0.7 cubic yards, and that moves by a third if the material or weather changes.

Density: the number every other calculator hides

Aggregate weight changes with the rock it was crushed from, the gradation, and how wet or compacted it is. The table below is what Caterpillar publishes in its earthwork volumes reference tables: loose weight, bank weight and the load factor between them.

The last three rows are yard charts from Marenakos Rock Center and North Bay Materials, describing material as delivered, damp; no load factor column because neither publisher gives one. Pea gravel, road base, decomposed granite, asphalt millings and riprap have no density at all: we could not open a document that publishes one, so the sheet asks for yours instead.

Compacted or loose: the conversion that changes the order

A base course is specified compacted, and sold loose off a conveyor: order the compacted number and you will be short. Caterpillar’s load factor is the ratio between the loose and the in-place weight of one cubic yard, so dividing by it converts an in-place volume into the loose volume to order. For gravel that factor is 0.89, so a compacted layer needs about 12 percent more loose material. Switch the toggle off when you measured a loose pile or a truck box already.

Read this before trusting the number. Caterpillar publishes loose and bank (natural, undisturbed) densities, not compacted ones. This sheet uses the bank figure as a stand-in for a compacted layer - a reasonable approximation for gravel, sand and soil, not a measured compaction factor. Override it if your supplier or spec gives one.

Crushed stone is the exception, and it is deliberate. Caterpillar's 4,500 lb/yd3 bank figure and 0.60 load factor describe solid rock in the quarry face before it is blasted, not a compacted base course, so neither is used for ordering here. Put your quarry’s bulking figure in the compaction allowance field if the spec is a compacted depth. The section drawing shows both states: the solid layer is the compacted depth, the dashed line above it is the loose depth that has to arrive to compact down to it.

Tons, tonnes and cubic yards

A short ton is 2,000 pounds, the US unit your local quarry means when it says “ton”. A metric tonne is 1,000 kilograms, which is 2,205 pounds: about 10 percent heavier. A cubic yard is not a weight, it is 27 cubic feet of space. This sheet prints all three so a quote in one unit can be checked against another.

Those are loose, finished depths. Compacted, add the load factor: 100 sq ft of compacted 4 inch base needs 1.39 cu yd loose, not 1.23.

Worked example: a 100 ft driveway at 4 inches

1. Area: 100 ft x 10 ft = 1,000 sq ft.
2. Depth: 4 in / 12 = 0.3333 ft, compacted.
3. In-place volume: 1,000 x 0.3333 = 333 cu ft = 12.35 cu yd.
4. Loose volume: 12.35 / 0.89 = 13.87 cu yd.
5. Order, rounded up to the half yard: 14 cu yd.
6. Weight at 2,850 lb/cu yd: 19.95 short tons.
7. Loads at 10 cu yd: 2.
8. At $42/ton: $837.9; at $58/cu yd: $812.

Add a 14 ft fire-pit circle at 3 inches — 154 sq ft, 1.6 more loose cubic yards — and it joins the same order.

Price per ton, truck loads and the takeoff

Quarries sell by the ton; landscape yards sell by the yard. Enter both and the sheet prices the order twice and names the cheaper one: on the driveway example, $42 per ton and $58 per cubic yard are only $25.9 apart on a 14 yard load. Delivery is usually a flat charge per load; a nearby yard can beat a cheaper quarry on the haul alone.

Loads are counted against a capacity you set, 10 cubic yards by default — ask what the truck is rated to carry legally, not what the box holds. Export CSV writes every line with a header carrying the sheet number, unit system and page URL; Print gives a one-page estimate with the drawings attached.

Frequently asked

How do I calculate how much rock I will need?

Multiply the area by the depth, both in feet, and divide by 27. A 100 by 10 ft driveway at 4 inches is 1,000 sq ft x 0.3333 ft = 333 cu ft = 12.35 cu yd in place. If compacted, divide by the 0.89 load factor for the loose volume to order: 14 cu yd, about 19.95 short tons.

How many cubic yards is 1 ton of gravel?

0.7 cubic yards for dry 1/4-2 in gravel, 0.59 for the same gravel wet, and 0.74 for crushed stone. There is no single conversion: it is 2,000 divided by the pounds per cubic yard of the material in front of you, which is exactly why this sheet shows the density it used and lets you replace it.

Is 3 cubic yards 3 tons?

No. Three cubic yards of dry gravel weighs 3 x 2,850 = 8,550 lb, which is 4.28 short tons. Yards and tons only match for a material weighing 2,000 lb per cubic yard, and almost no aggregate does: mulch is lighter, every gravel is heavier.

Limits of this sheet

C-101 calculates volume, weight, loads and material cost for a layer of aggregate. It does not design a base course, check bearing capacity, or size a gradation. Every density is a published figure for a material like yours, not a measurement of the pile you are buying; the truck capacity (10 cu yd) and the 0.5 cu yd rounding are this sheet’s assumptions, both editable. Caterpillar publishes loose and bank (natural, undisturbed) densities, not compacted ones. This sheet uses the bank figure as a stand-in for a compacted layer - a reasonable approximation for gravel, sand and soil, not a measured compaction factor. Override it if your supplier or spec gives one. caterpillar's 4,500 lb/yd3 bank figure and 0.60 load factor describe solid rock in the quarry face before it is blasted, not a compacted base course, so neither is used for ordering here. Quantities are for planning and ordering, not engineering.