Order too little aggregate and the job stops; order too much and you pay to haul it away. This calculator turns an area and a depth into the volume and weight of gravel, crushed stone, sand, or decomposed granite you actually need, in both imperial and metric units.
How it works
Volume is area times depth, converted to cubic yards, and weight comes from the material’s bulk density:
volume (cu ft) = length ft × width ft × (depth inches / 12)
cubic yards = volume cu ft / 27
cubic metres = cubic yards × 0.7646
tons = cubic yards × density (tons per cubic yard)Each material carries its own bulk density, so changing the material changes the tonnage even when the footprint is identical.
Worked example — residential gravel driveway
A 30 ft by 12 ft driveway to be covered with 4 inches of crushed stone:
- Area = 30 × 12 = 360 sq ft
- Volume = 360 × (4/12) = 120 cu ft
- Cubic yards = 120 / 27 = 4.44 cu yd
- At approximately 1.4 tons per cubic yard: 6.2 tons
- With 15% compaction allowance: order about 7.1 tons
In practice, suppliers sell by the ton and deliver by the truckload. A standard single-axle dump truck carries approximately 12 to 14 tons; a tandem-axle carries 16 to 20 tons. At 7 tons for this driveway, a single smaller truck covers the project with room to spare.
Recommended depths by application
Depth requirements vary significantly by use case. Getting this wrong is the most common mistake — a gravel surface that is too shallow ruts and migrates under load:
| Application | Minimum depth | Notes |
|---|---|---|
| Decorative path | 2 inches | Light foot traffic only |
| Garden path (regular use) | 3 inches | Compact base first |
| Residential driveway | 4–6 inches | 4” top course over a compacted sub-base |
| Commercial or heavy vehicle area | 6–8 inches | Often requires engineered base course |
| French drain / drainage trench | Fill to design depth | Varies by drainage capacity needed |
For driveways and any area with vehicle traffic, the standard approach is to separate the material into two lifts: a coarser 3/4-inch or crusher-run base layer compacted first, then a finer top dressing of pea gravel or crushed stone on top. This tool lets you calculate each layer separately if you want to order the two materials independently.
Why bulk density varies by material
The same cubic yard of space holds different weights depending on the material:
- Pea gravel (rounded, small): slightly lighter, packs less efficiently
- Crushed stone (angular, 3/4 inch): angular edges interlock, similar to gravel
- Sand (fine particles): settles more densely, so more weight per cubic yard
- Decomposed granite (fine, angular): intermediate density
When you switch between materials in this tool, the tonnage changes even though the volume is the same. This matters for ordering: suppliers quote by weight (tons), so matching the material’s density to the correct rate avoids ordering the wrong amount.
Compaction allowance
Aggregate delivered loose always compacts when rolled or driven over, typically by 10–20% in depth. To end up with a 4-inch finished compacted surface, order material calculated for roughly 4.5 to 4.8 inches of loose depth. The standard rule of thumb is to add about 15% to the calculated volume before ordering. This tool calculates the design volume; add the compaction buffer when you place the order.