Gravel Calculator

The basic gravel calculation follows the same geometry as concrete: Volume = Length × Width × Depth. The critical additional step is converting volume to weight, since suppliers sell by the ton. The U.S. Geological Survey (USGS) publishes density data for construction aggregates in their Minerals Yearbook.

Volume Calculation Steps

Step 1: Measure the area in feet (length × width for rectangles, π × r² for circles). Step 2: Convert desired depth to feet (divide inches by 12). Step 3: Multiply area × depth = cubic feet. Step 4: Divide by 27 = cubic yards. Step 5: Multiply cubic yards by the gravel's density factor for tons.

Gravel Density by Type

Note that lava rock is nearly half the density of most gravel — you need the same volume but roughly half the weight, making it significantly cheaper per area covered.

The correct depth depends on the project type, traffic load, and base preparation. The American Society of Landscape Architects (ASLA) and the Interlocking Concrete Pavement Institute (ICPI) provide depth guidelines for different applications.

Depth Recommendations by Project

The Three-Layer Driveway System

Gravel driveways perform best with three compacted layers, as recommended by university extension services and the National Stone, Sand & Gravel Association (NSSGA): Bottom layer (4") — large crushed stone (#3 or #4, 1.5–2.5") for drainage and stability. Middle layer (2–3") — mid-size stone (#57, 3/4–1") for load distribution. Top layer (2–3") — angular crushed stone (#8 or #411) with fines that compact into a solid, walkable surface. Each layer should be compacted with a roller or plate compactor before adding the next.

Gravel pricing varies significantly by type, quantity, and delivery distance. The USGS reports the average producer price for construction sand and gravel at $12.20 per metric ton, though retail prices to consumers are considerably higher due to processing, transportation, and retail markup.

Retail Pricing Guide (2024)

Bulk vs Bags: The Cost Comparison

Buying in bulk (by the ton or cubic yard) is dramatically cheaper than bags for projects over 0.5 cubic yards. A ton of pea gravel in bulk costs $25–$55, while the equivalent from 50 lb bags at Home Depot costs approximately $225–$300 (54 bags × $4.50–$5.50). That's a 4–6× price premium for bags. Most landscape supply yards offer delivery for $50–$150 depending on distance, still far cheaper than bagged material for projects requiring more than a few hundred pounds.

#57 Crushed Stone

The most popular gravel for driveways and drainage, #57 stone is 3/4" to 1" angular crushed rock. The number comes from the ASTM C33 aggregate sizing standard — sieve #5 (1") through sieve #7 (3/4"). Its angular shape locks together when compacted, creating a stable surface that doesn't shift under tire weight. The NSSGA rates #57 as the highest-volume gravel product in the U.S.

Pea Gravel

Small, smooth, rounded stones (1/4" to 3/8") in natural earth tones. Pea gravel is excellent for walkways, patios, and between pavers because it's comfortable underfoot. However, its rounded shape means it doesn't compact well — it shifts under heavy loads, making it a poor choice for driveways unless contained by edging. Cost-effective and widely available at Home Depot, Lowes, and landscape suppliers.

3/4" Clean Gravel

Single-size clean gravel without fines (dust). Used primarily for drainage applications: french drains, retaining wall backfill, and septic leach fields. The consistent size prevents compaction, maintaining water flow pathways. The EPA's stormwater management guidelines recommend 3/4" clean gravel for permeable drainage systems.

Decomposed Granite (DG)

Finely crushed granite that compacts into a semi-solid surface — popular for paths, xeriscaping, and rustic landscapes in the western U.S. Three grades exist: natural DG (loose, needs reapplication), stabilized DG (with binding agent for harder surface), and resin-coated DG (most durable, permeable). The ASLA's sustainable landscape guide recommends DG as a permeable paving alternative that reduces stormwater runoff.

Always Use Landscape Fabric

Landscape fabric (geotextile) between the soil and gravel prevents mixing and weed growth. The Geosynthetic Institute recommends non-woven geotextile for gravel applications — it allows water drainage while blocking soil migration. Without fabric, gravel gradually sinks into soft soil, requiring costly reapplication every 2–3 years instead of the expected 5–10 year lifespan.

Edging Contains Gravel Migration

Without proper edging, gravel spreads into adjacent lawn and garden areas. Options include steel edging (most professional, $2–$4/linear foot), plastic edging ($0.50–$1.50/ft), stone borders, or pressure-treated timber. The ICPI specifically recommends rigid edge restraint for all aggregate surfaces to maintain design intent.

Compaction Is Non-Negotiable for Driveways

Each layer of driveway gravel must be compacted with a plate compactor (rent for $75–$100/day at equipment rental centers). The FHWA (Federal Highway Administration) road construction standards require 95% compaction density for gravel road surfaces. For DIY driveways, run the plate compactor over each layer 3–4 passes in alternating directions. Water the gravel lightly before compacting for better results — moisture helps particles settle into maximum density.

Drainage: Grade Away From Structures

All gravel surfaces should be graded to direct water away from buildings at a minimum 2% slope (1/4 inch per foot), per IRC R401.3 grading requirements. Poor drainage under gravel causes frost heave in cold climates and erosion in rainy climates. Installing a french drain beneath gravel driveways captures and redirects water, extending the driveway's lifespan significantly.