The math behind the material.

Volume comes first

For a rectangular area, volume = length × width × depth. For a circle, volume = π × (diameter ÷ 2)² × depth. For a known surface area, volume = area × depth. The calculator converts each input into meters before calculating, then sums the volumes of all areas.

In US units, length (ft) × width (ft) × depth (in) ÷ 324 gives cubic yards. In metric units, area (m²) × depth (cm) ÷ 100 gives cubic meters.

Bulk density and weight

Weight = purchase volume × bulk density. The initial value of 105 lb/ft³ is a general estimate, not a specification for pea gravel, crushed stone or any particular product. It converts to approximately 1,682 kg/m³. You can replace it with your supplier’s value or remove it to calculate volume only.

Bulk density includes the voids between particles. Do not substitute solid rock density. Moisture, particle shape and grading affect the result. Omni Calculator’s gravel reference also uses approximately 105 lb/ft³ as a general gravel estimate; the supplier’s product data should take precedence.

Material references, not universal densities

The pea gravel preset uses Lasalle Sand & Gravel’s published 2,700 lb per cubic yard (100 lb/ft³). The 3/4-inch crush-minus preset uses that supplier’s 2,600 lb per cubic yard (approximately 96.30 lb/ft³). These are references for specific products, not specifications for every quarry. No supplier prices are imported.

Source: Lasalle’s material weight and conversion table, checked September 16, 2026. For comparison, South Bay Materials lists its 3/8-inch pea gravel at 2,440 lb per cubic yard. Differences between products are why your supplier’s value takes precedence.

Choosing a preset sets bulk density. Editing that density marks the material as custom. Unit changes preserve the physical density; shared estimates preserve the selected reference and inputs. No reference in this tool constitutes an endorsement or supply relationship.

Known volume

If you already know your quantity, choose Known volume and enter cubic yards in US mode or cubic meters in metric mode. No depth is required. The same allowance, density, bag and cost calculations apply. Do not add a known volume and dimensions for the same material area, which would count it twice.

Extra allowance is explicit

Purchase volume = geometric volume × (1 + allowance ÷ 100). The default is 0%. The calculator does not select a waste or compaction percentage for you. Ask the supplier how a compacted design layer translates to loose material before ordering.

Units and conversion factors

See the NIST Guide to the SI conversion tables. Internal calculations retain precision; the main results are displayed to two decimal places. Supplier order increments are not automatically applied.

Bags and quoted costs

Volume bags = purchase volume ÷ volume per bag. Weight bags = estimated weight ÷ weight per bag. The calculator rounds the bag count up to a whole bag. A small numerical tolerance prevents floating-point conversion noise from adding a bag to an exact whole-bag result.

Cost = quantity × your unit quote + delivery. The quantity is cubic yards, cubic meters, short tons, tonnes or whole bags, depending on your selection. All cost fields use USD. Tax, labor, equipment, minimum orders and supplier rounding are excluded.

A reproducible example

20 ft × 10 ft × 3 in = 50 ft³ = 1.851851… yd³. At 105 lb/ft³ that is 5,250 lb, or 2.625 US tons. Dividing by 0.5 ft³ per bag gives exactly 100 bags. A 10% allowance changes the volume to 55 ft³ and the bag count to 110.

How the homepage reference tables are calculated

The tables use the same calculation functions as the interactive tool, with 105 lb/ft³, no extra allowance and no compaction. The yard table starts from known cubic yards. Coverage per US ton is the reciprocal of the calculated tons needed for one square foot at the selected depth. The area table calculates each area and depth, then rounds the 0.5 ft³ bag count up. Tables are static examples and do not respond to changes in the calculator.

Calculation checks and corrections

Automated checks cover known rectangle and circle examples, multiple areas, known volume, whole-bag rounding, invalid inputs and US-to-metric conversion invariants. Browser checks cover completed calculations, sharing and mobile use. These are software checks, not an independent engineering review or verification of your supplier’s material.

To report a discrepancy, include the dimensions, units, bulk density, allowance and expected result. You can copy these from the order summary. Confirm any unresolved discrepancy with your supplier before ordering.

Scope and limits

This tool estimates material quantities. It does not design structural layers, drainage or a driveway. Use separate estimates for different materials. Measure an irregular area as smaller shapes, avoid double counting overlap and check the final specification with your supplier or installer.