Rock & Stone Calculator

How to use

1. Enter your area as a rectangle, circle, triangle, or type in a square footage you already know.
2. Pick a rock size, such as 3/4 inch, 1-2 inch or 2-4 inch: the calculator suggests a depth using the depth-by-rock-size guide below, or choose a project preset like driveway, path or drainage instead.
3. Choose a rock or stone type from the material list. Each type has its own typical weight per cubic yard.
4. Adjust the depth if your project needs more or less coverage than the suggestion.
5. Read the result: cubic yards, tons, bag count, coverage per ton, and an order line rounded to what a supplier actually sells.

How it works

The volume math matches the other calculators on this site: length times width times depth for a rectangle, or the matching formula for a circle or triangle, with depth converted from inches to feet, then the total divided by 27 to turn cubic feet into cubic yards. Weight comes from multiplying cubic yards by the density of the rock type you picked, in tons per cubic yard, using a typical value plus a minimum and maximum, because rock density changes with the stone’s size, shape and moisture.

The depth-by-rock-size suggestion comes from landscape rock suppliers’ depth guides: lay decorative rock at about twice the average stone size, so the gaps between pieces are covered and no bare ground or fabric shows through. Bigger, more rounded stone needs the deeper end of that guidance: its gaps are larger, which is why the rock-size presets above step up from 2-3 inches for small stone to 3-8 inches for large stone. Even the smallest rock keeps a 2 inch floor. That’s the practical minimum for ground cover, no matter how fine the stone is.

As with the other tools, two adjustments matter for a real order: an extra percentage for waste and settling that varies by rock type, and rounding: the order line rounds volume up to the next half cubic yard, weight up to the next half ton, and bag counts up to a whole bag. Coverage per ton works in reverse: it divides one ton by the density to estimate the square footage one ton covers at your chosen depth.

Limits: this assumes a flat area at one constant depth, so a sloped bed or an uneven dry creek bed needs more rock than the flat math suggests. Add a separate area for the low spot instead of applying one depth across the whole space. Rock size classes like “1-2 inch” describe a range of stone sizes within a shipment, not one exact size, so treat the depth suggestion as a starting point and check coverage once the rock is spread, because porous or unusually shaped stone can settle differently than smooth, dense rock.

Depth by rock size

Landscape rock suppliers’ depth guides put the right depth at about twice the average stone size, so bigger stone needs a deeper layer to cover the gaps between pieces.

For driveway, path, patio base, drainage or decorative-cover projects instead of a rock-size pick, use the matching preset; the gravel calculator’s depth guide has the full breakdown for those project types.

Worked example

1. Area: 14 ft × 6.5 ft = 91 sq ft
2. Depth: 3 in ÷ 12 = 0.25 ft
3. Volume: 91 sq ft × 0.25 ft = 22.75 cu ft
4. Extra for settling: 22.75 cu ft × 1.10 = 25.03 cu ft
5. Cubic yards: 25.03 ÷ 27 = 0.93 cu yd (0.71 m³)
6. Weight: 0.93 cu yd × 1.35 tons per cu yd = 1.3 tons (1.1 tonnes)
7. Order: round up to 1.5 tons, or 51 bags of 0.5 cu ft

Questions people ask

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