Stone Calculator

Enter your area dimensions, pick your stone type, and get instant volume, weight, and bulk bag totals.

How to Calculate Stone for Any Project

Stone quantities come down to three measurements: the area you're covering, the depth you want, and the density of the material. Multiply those together and you get volume. Apply the stone's density and you get weight. This calculator handles all of that, then adds your chosen overage allowance so you're not making a second order run.

For rectangular areas, the formula is straightforward: length times width times depth (converted to feet) divided by 27 gives cubic yards. For circular areas, use pi times the radius squared times depth. Weight in tons is the cubic footage multiplied by the stone's density in lb/ft³, divided by 2000.

Choosing the Right Stone Type

Crushed stone is the go-to for driveways, base layers, and anywhere compaction matters. At around 105 lb/ft³, it packs down well and locks in place. River rock is smooth and rounded, which makes it popular for drainage channels, garden beds, and decorative ground cover. Lava rock is considerably lighter at about 50 lb/ft³, which reduces delivery weight and makes it easier to move around, though it's mostly used for aesthetics rather than structural purposes.

If your supplier provides a specific density for the product they're selling, plug it into the custom density field. Stone products vary more than most people expect, and using the actual spec will give you a tighter estimate.

How Much Overage to Add

A 10% overage is standard for most jobs. It covers minor spillage, uneven sub-grades, and the fact that stone settles after installation. For irregular shapes or areas with multiple cut-ins, go to 15%. For simple, flat rectangular areas with clean edges, 5% may be enough. Ordering short and making a second trip almost always costs more than the extra material.

Depth Guidelines by Application

Walkways generally need 2 to 3 inches of stone. Driveways need at least 4 inches, with a compacted base beneath. Decorative borders or ground cover can work at 1 to 2 inches. Drainage applications typically call for 6 inches or more, depending on the volume of water being managed. If you're laying stone over existing material, measure the depth you're adding, not the total depth.

Bulk Bags vs. Bulk Delivery

Bulk bags (also called tonne bags or jumbo bags) typically hold around 0.5 cubic yards each and are convenient for small to medium jobs where a dump truck isn't practical. For anything over 5 cubic yards, bulk delivery by the ton almost always works out cheaper per unit, and the supplier can drop the material exactly where you need it. Get quotes both ways if your job sits in the 3 to 6 cubic yard range.

Frequently Asked Questions

Each bulk bag holds about 0.5 cubic yards, so 1 cubic yard requires 2 bags. That's a rough guide though. Confirm the bag size with your supplier before ordering, as capacity varies by product.
A US ton (short ton) is 2,000 lb. A metric tonne is 1,000 kg, which equals about 2,205 lb. They're close but not the same. US suppliers quote in tons; most metric countries quote in tonnes. If you're unsure which your supplier uses, just ask.
Yes. Select the custom density option and enter the density for your specific material. Pea gravel runs around 100 lb/ft³, coarse sand around 110 lb/ft³. Your supplier's product data sheet will have the exact figure.
The base calculation gives you the theoretical minimum. In practice, stone settles under foot traffic and load, sub-grades are rarely perfectly flat, and some material is always lost to spillage during installation. The overage factor builds that buffer into your order total so you order enough the first time.
Break the area into smaller rectangles or circles, calculate each one separately, then add the totals together. For odd curves, a rough rectangle that slightly overshoots the boundary is a good working estimate. Set your overage to 15% or 20% to cover the inaccuracy.
Compaction is handled through the overage allowance. Loose stone compacts about 10 to 20% after installation, which is why the 10% standard overage exists. For driveways that will carry vehicle loads, use 15% to be safe.

Stone Project Planning Checklist

Before placing your order, check excavation depth, confirm sub-grade condition, verify drainage slope, and arrange delivery access. The checklist below covers the steps most people miss.

Download Checklist (PDF)

Planning use only. See Methodology and Data Sources. View all project checklists →

Accuracy & Review

Reviewed by: Maria Ramirez, PE

Maria is a licensed Professional Engineer with experience in residential and light commercial concrete quantity takeoffs. She reviewed the volume formulas, unit conversions, bag yield assumptions, and waste factor guidance used in this calculator.

Last updated:

See: Methodology · Data Sources · Review Board

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Disclaimer

These calculations are general planning estimates only. Actual quantities may vary due to compaction rates, settlement, moisture content, excavation depth, and site-specific conditions.

Base preparation, drainage requirements, and load-bearing needs may alter total material requirements. Always confirm quantities with your supplier before ordering.

See our Methodology and Data Sources for details.