How the Gravel Calculator Works
The math is straightforward: volume = length × width × depth. Weight = volume × density. The Microapp calculator handles the unit conversions (US ↔ metric, feet/inches ↔ meters/centimeters), the density lookup for different gravel types, and the conversion to industry-standard units (cubic yards, short tons, metric tonnes) that suppliers actually quote prices in.
• Volume in cubic feet: 30 × 10 × (4/12) = 100 ft³
• Volume in cubic yards: 100 / 27 = 3.7 yd³
• Weight (crushed stone density 100 lb/ft³): 100 × 100 = 10,000 lb ≈ 5 short tons
• Order 10% extra for settling: 5.5 tons total
Common Gravel Types and Their Densities
| Type | Density (lb/ft³) | Density (kg/m³) | Best for |
|---|---|---|---|
| Pea gravel | ~105 | ~1,682 | Paths, playgrounds, decorative; smooth and rounded |
| Crushed stone | ~100 | ~1,602 | Driveways, base layers; angular, locks together |
| River rock | ~95 | ~1,522 | Drainage, decorative borders; large 1-3" smooth stones |
| Decomposed granite | ~106 | ~1,700 | Garden paths, patios; compacts firmly |
| Sand | ~100 | ~1,602 | Bedding under pavers, playgrounds |
| Limestone | ~97 | ~1,554 | Driveways, agricultural use; lighter color |
Densities are approximate and depend on moisture content, particle size, and how compacted the gravel is. Suppliers' actual densities can vary 10% from these values; the calculator uses widely-accepted averages.
Recommended Depths by Project Type
| Project | Depth (US) | Depth (metric) | Notes |
|---|---|---|---|
| Decorative cover (planters, garden beds) | 2-3 in | 5-7 cm | Just enough to cover soil and suppress weeds |
| Walking path | 3-4 in | 7-10 cm | Compacts under foot traffic; deeper sinks too much |
| Driveway base layer | 4-6 in | 10-15 cm | Over a compacted base of crushed-rock subgrade |
| Driveway surface (over base) | 2-3 in | 5-7 cm | Pea gravel, river rock, or decorative top coat |
| Heavy-traffic road / parking | 6-12 in | 15-30 cm | Multiple compacted lifts; engineered specs |
| French drain backfill | full trench depth | — | Fill from pipe to ground level |
Why Order Extra
Gravel settles as it's installed and used. Loose gravel poured at 4 inches settles to about 3.5 inches once cars drive over it or it absorbs rainfall. To finish at 4 inches, order enough for ~4.5 inches.
The standard rule: add 5-10% to your calculation. 5% for contained applications (raised beds, walled paths), 10% for unbounded ones (driveways, open paths) where some gravel migrates outside the working area.
Better to have a small leftover pile than to come up short and need a second delivery (which usually has a minimum-order or delivery fee).
Pricing — How Suppliers Quote Gravel
Three pricing models, varies by region and supplier:
- By the ton. The most common — suppliers quote per short ton (2,000 lb) in the US, per metric tonne (1,000 kg) elsewhere. Buy by weight; loaded into your truck or delivered.
- By the cubic yard. Some suppliers (especially landscape supply yards) sell by volume, particularly for decorative gravels. A "yard of gravel" = 1 cubic yard ≈ 1.4 short tons.
- By the bag. Big-box stores sell gravel in 0.5 cu ft bags (about 50 lb each) for small DIY projects. Expensive per-unit but practical when you need just a few square feet.
For projects over 1 cubic yard, bulk delivery is almost always cheaper than bagged. Below 1 yd³, bagged might be more economical (no delivery fee, no minimum order).
Common Pitfalls
Mixing units. Length in feet, depth in inches — always convert depth to feet (divide by 12) before multiplying. Or use the calculator, which handles units automatically.
Forgetting the base layer. Driveways need a compacted aggregate base under the visible gravel layer. The "depth" you order should be just the surface gravel, not the base — but you also need to budget for base material separately.
Underestimating slope. If your area slopes, the actual volume needed is slightly more than the flat-area calculation. For slopes greater than 5%, multiply by 1.05-1.1 to compensate.
Density assumptions. If your supplier uses different densities (some quote based on loose, others based on compacted), the weight conversion may be off. Confirm with the supplier when ordering by ton vs. by yard.
Related Tools
For computing volumes of cylindrical containers (water tanks, drums, etc.), use the Volume of a Cylinder calculator. To compute the area of a triangular section before extruding to a volume, see the Area of a Triangle tool. For broader unit conversion across length, weight, area, and volume, the Unit Converter handles them all.