How Many Tons of Gravel Do I Need?

Two different questions hide inside “how much gravel do I need?”

• How much space will it fill? That is volume. It is measured in cubic feet and cubic yards, and the math is exact.
• How much will it weigh? That is weight. It is measured in tons, and it depends on the material. There is no single true number.

Work the volume first. Then turn the volume into a range of tons, using the official test figures explained below.

Calculator: volume exact, tons as a range

Type in the size of the area and how deep the layer will be. Nothing is sent anywhere — the math runs on this page, on your device.

The tons figures come from tests run for the Wisconsin Department of Transportation. Loose gravel — as it sits in a pile or a truck — was weighed dry at 90 to 104 pounds per cubic foot for the dense graded base gravels tested. Packed-down (compacted) aggregate was converted at 1.50 to 1.98 tons per cubic yard across every aggregate tested. The sections below explain both figures.

How the volume math works

Texas A&M AgriLife Extension gives the basic formula this way: total cubic yards = (length in feet × width in feet × (depth in inches ÷ 12)) ÷ 27.

• Step 1 — Area. Length × width gives square feet.
• Step 2 — Depth in feet. Depth in inches ÷ 12 gives depth in feet, so all three numbers use the same unit.
• Step 3 — Cubic feet. Area × depth in feet gives cubic feet.
• Step 4 — Cubic yards. Cubic feet ÷ 27 gives cubic yards. One cubic yard holds 27 cubic feet.

Extension’s own worked example: an area 10 feet long by 10 feet wide, covered 3 inches deep, needs 0.93 cubic yards — which they round up to 1 yard. Extension also advises rounding your result up to the nearest yard or half yard, depending on how you are purchasing the material.

For that same 10 by 10 foot area at 3 inches deep, the calculator above gives about 1.1 to 1.3 tons if the layer stays loose, and about 1.4 to 1.8 tons if the same layer is packed down. Same space. Different weight. The next section explains why.

Why the weight is a range, not one number

The material itself differs. The U.S. Geological Survey (USGS) explains that crushed stone and sand and gravel are the two main sources of natural aggregates. Sand and gravel deposits are commonly the result of bedrock weathered and then moved and laid down by water or ice, so they are often found as river or stream deposits or in glaciated areas. Crushed stone comes from a wide variety of parent bedrock. Limestone and other carbonates account for approximately three quarters of the rocks used for crushed stone, with granite and other igneous rocks making up the bulk of the remainder. Different rock, different deposit, different weight for the same space.

Loose is not packed. The Wisconsin Department of Transportation research describes three states for these materials: bank (in the ground), loose (stockpile or hauling), and compacted (placed and packed). The same material takes up more room loose than packed. For the aggregates tested, the loose volume for the same weight was 27% to 60% larger than the compacted volume. That is why this page shows two tons ranges, not one:

• Loose, dry: 90 to 104 pounds per cubic foot, measured by a unit box test on 1¼-inch and ¾-inch dense graded base. That works out to about 1.22 to 1.40 tons per cubic yard (pounds per cubic foot × 27 ÷ 2,000 pounds per ton).
• Packed down: 1.50 to 1.98 tons per cubic yard of compacted volume, across every aggregate tested — from backfill material at the low end to dense graded base at the high end. Dense graded base alone tested at 1.78 to 1.98 tons per cubic yard.

Water adds weight. The Wisconsin loose and packed figures above are dry unit weights — they do not count water held in the pile. Across the aggregates tested loose, moisture ran about 2% to 7%. A wet load weighs more than the same load dry. A California conversion table used by CalRecycle makes the same point for soil: it lists dry soil at 2,025 pounds per cubic yard and wet soil at 2,106 pounds per cubic yard.

Why official numbers do not all agree

Online calculators often print one neat factor, as if it were settled. The official record is not settled, and this page will not pretend it is.

• The CalRecycle table lists stone or gravel at 2,632.5 pounds per cubic yard — about 1.32 tons. That single general figure falls inside the Wisconsin loose range above.
• The Wisconsin tested packed-down factors run 1.50 to 1.98 tons per cubic yard — higher, because packed material has less air in it.
• Wisconsin’s older statewide table for compacted granular materials runs wider still in places: dense graded base is listed at 1.75 to 2.1 tons per cubic yard for ¾-inch, 1.75 to 2.0 for 1¼-inch, and 1.75 to 2.2 for 3-inch.
• In the Wisconsin survey of state transportation departments, only about 23% of the departments that answered provided conversion factors for aggregates at all. The report found that practice relies heavily on personnel experience and a wide variety of methods.

So a range is the honest answer. Anyone who gives you one exact tons figure for “gravel” without naming the exact material, its moisture, and whether it is loose or packed has left out the parts that move the number.

The supplier’s ticket is the actual tons

Conversion tables are the backup tool, not the main one. The Los Angeles County guidelines that carry the CalRecycle table say the table “should be used as a tool when material cannot feasibly be weighed.” In other words, weighing comes first. The same county paperwork runs on weight tickets that list the tonnage of each load.

When gravel is sold by the ton, the load is weighed and the ticket states the tons. That ticket figure — for your exact material, on that day — is the weight you pay for. A calculator range helps you plan and helps you check that a quote is in a sensible range. It does not replace the ticket.

Before you order, ask the supplier:

• What is your tons-per-cubic-yard figure for this exact material?
• Is that figure for the material loose, or packed down?
• Will the total come from a scale ticket for my load?
• Do you sell by the ton, by the whole yard, or by the half yard?
• How much extra, if any, do you suggest for my project — and why?

Bring your cubic yard figure from the calculator. Let the supplier convert it with their own figure for their own material, and compare it with the range on this page.

This page does not tell you how deep to make a layer. Use the depth in your project plan, or the depth your supplier or local code calls for, and type that depth into the calculator.