Free Calculator · Published November 2026
Stone Calculator for Cubic Yards
A stone calculator multiplies length by width by depth in feet and divides by 27. A 12 by 20 foot area at 4 inches deep is 80 cubic feet, or 2.963 cubic yards. Pounds stay blank until you type them. The USDA rock figure of 2.65 grams per cubic centimeter is solid rock, not a loose pile.
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Book a DemoHow the Stone Calculator Counts Volume
Depth in inches is divided by 12. Cubic yards are cubic feet divided by 27. Square feet are length times width, for flagstone laid as a surface.
Starts blank. 2.65 g/cm³ is not filled in.
Your allowance for flagstone cuts. Not a standard percent.
80.000 cubic feet = 2.963 cubic yards. Area is 240.0 square feet.
No cut allowance is applied until you type a percent.
Weight is blank until you type pounds per cubic foot.
All calculations are estimates based on historical information and should be verified by the user.
Important: weight is optional
All calculations are estimates based on historical information and should be verified by the user. This tool is provided as a free service for planning purposes only and is not a substitute for a professional assessment, a supplier quote, or applicable local code requirements.
What the Stone Calculator Leaves Blank
Landscape stone and flagstone are ordered as yards or as square feet. A driveway of pea gravel or number 57 stone is a different job, on the gravel calculator. Bedding sand is the sand calculator. This page does not apply the tons-per-yard figures from either one.
Worked volume
Length 12 feet. Width 20 feet. Depth 4 inches, which is 4 ÷ 12 feet. 12 × 20 × (4 ÷ 12) = 80 cubic feet. 80 ÷ 27 = 2.963 cubic yards at three decimals. The footprint is 240 square feet. With the cut allowance left blank, the area stays 240.
| Step | Figure |
|---|---|
| Square feet | 240 |
| Cubic feet | 80 |
| Cubic yards at three decimals | 2.963 |
| Pounds | Blank |
2.65 is the rock, not the pile
The USDA bulk-density guide says rocks generally have a density of 2.65 grams per cubic centimeter. A later note says the default value of 2.65 is a rule of thumb based on the average bulk density of rock. The guide divides a soil bulk density by 2.65 to estimate porosity. Pieces in a truck have air between them. That air is why a pile weighs less per cubic yard than solid rock. This stone calculator does not invent the missing air percent.
Compacted ranges, not a default
FHWA Table 5-17 lists compacted dry unit weights after Carter and Bentley, 1991. The ranges are wide. A midpoint would hide that. None of these numbers is placed in the weight box.
| Compacted mixture | lb/cu ft |
|---|---|
| GW, well-graded clean gravel/sand | 125–134 |
| GP, poorly graded clean gravel/sand | 115–125 |
| GM, well-graded, small silt content | 119–134 |
| GC, well-graded, small clay content | 115–125 |
How should you write the stone order?
- Length, width, and depth, with the unit on each.
- Cubic feet, then cubic yards as cubic feet divided by 27.
- Square feet, and any cut percent you typed yourself.
- Whether weight was left blank.
- If you typed pounds per cubic foot, where that number came from.
- A note that 2.65 grams per cubic centimeter was not converted, and that the gravel-page densities were not used.
Flagstone is an area
Irregular flagstone is sold by the square foot or by the pallet that covers a square-foot claim. The depth box is for a bed of loose stone. If you are only covering a surface, use the square feet and ignore the yards, or set the depth to the thickness you are actually placing. Paver counts stay on the paver calculator. Odd shapes can be added as cubic feet on the cubic yard calculator before you divide by 27.
Frequently Asked Questions
How much stone does the stone calculator count?
Multiply length in feet by width in feet by depth in feet, then divide by 27. A 12 by 20 foot area at 4 inches is 80 cubic feet, which is 2.963 cubic yards at three decimals. The same footprint is 240 square feet before any cut allowance you type.
Why is 2.65 not the stone calculator weight?
USDA's May 2019 bulk-density guide says rocks generally have a density of 2.65 grams per cubic centimeter, and it uses 2.65 as a rule of thumb for the average bulk density of rock inside a porosity formula. That is solid rock, not the air between pieces in a pile. This page does not convert 2.65 into tons.
Does the stone calculator use the gravel densities?
No. Pea gravel, crushed stone number 57, and the tons-per-yard figures on the gravel calculator stay on that page. This stone calculator leaves pounds blank until you type a unit weight.
What are the FHWA gravel ranges on this page?
FHWA Table 5-17 lists compacted dry unit weights for gravel and sand mixtures. Well-graded clean material, GW, is 125 to 134 pounds per cubic foot. Those ranges are compacted pavement soils. The box does not pick a midpoint. Type a number only when it matches the material you are ordering.
Save the Stone Calculator Yards
The cubic yards, the square feet, and a blank weight line belong on the proposal.
Get a Free DemoAll calculations are estimates based on historical information and should be verified by the user. This tool is provided as a free service for planning purposes only and is not a substitute for a professional assessment, a supplier quote, or applicable local code requirements.