Where do your density figures come from?

Quarry-published spec sheets from major U.S. aggregate producers (Vulcan Materials, Martin Marietta, Lehigh Hanson) cross-checked against USGS Mineral Commodity Summaries and ASTM D2940 / D448 grading specifications. The range shown for each material reflects the variation across sources; the average is what the calculator uses.

How accurate are the calculator's results?

Volume math is exact — the formulas are standard geometry and the constants are unit conversions. Weight estimates depend on the material's true density, which varies ±5% by source quarry, moisture content, and gradation. With the default 10% buffer applied, you'll be within a small-bag margin of correct on a well-measured project.

Can I use these calculations for commercial or structural work?

The calculations are appropriate for residential and small-commercial DIY work, contractor estimates, and homeowner planning. For structural concrete, retaining walls over 4 ft tall, and any project requiring an engineering stamp, follow your engineer's design rather than these volumetric estimates. The references section above lists the codes that govern professional work in each category.

How often is the methodology updated?

Density figures and standards are reviewed every 18 months. Pricing-sensitive content (referenced from the cost guides) is reviewed annually. Calculator math has been stable since launch — formulas don't change. When industry standards revise (e.g., AASHTO, ASTM), we update the references and adjust calculator defaults if needed.

Why do my supplier's tonnage numbers differ from the calculator?

Three reasons: (1) Your supplier may use a different density assumption — ask which spec they're quoting against. (2) Moisture content adds 3–8% weight to wet stone. (3) Some suppliers quote loose volume (uncompacted) while the calculator estimates the compacted equivalent. Differences under 10% are normal and within both estimates' expected accuracy.

Can I cite this methodology page in a contractor proposal or report?

Yes. The page is intentionally written to be citable: every formula and constant is sourced, every density has a citable industry reference, and the page displays its last review date. Use the URL plus the review date as your citation. For permission to reproduce the full density table or formulas in a published work, email press@calculategravel.com.

Methodology: Formulas, Densities & Assumptions

The exact formulas, density values, and assumptions our gravel calculator uses, with citations to ASTM, USGS, and quarry-published spec sheets.

We publish our calculator's math openly so you can verify it. Every output you see on this site comes from the formulas and constants below — there's no fudge factor and no proprietary black box.

Our principles

Show the math. The formulas are public. The density table is public. If you disagree with a number, the calculator's material picker lets you check the range.
Round at the boundary, not in the middle. Internal calculations are done in cubic feet at full floating-point precision. We round only at the display stage.
Conservative buffers. The default 10% waste buffer is standard industry practice for residential gravel projects.
Citations matter. Densities are stated as ranges, not single numbers, because real-world gravel varies with source and moisture.

Volume formulas

All volume math is done in cubic feet. Lengths convert to feet at the input boundary (inches divide by 12; meters multiply by 3.281).

Shape	Formula
Rectangle	L × W × D
Circle	π × (diameter / 2)² × D
Triangle	0.5 × base × height × D
Annulus (ring)	π × ((outer/2)² − (inner/2)²) × D
Multi-area	Σ (area_i) × D

Unit conversions

Conversion	Exact value
1 cubic yard	27 cubic feet
1 cubic meter	35.3146667 cubic feet
1 inch	1/12 ft (0.0833 ft)
1 foot	0.3048 m
1 short ton (US)	2,000 lb (907.185 kg)
1 metric tonne	1,000 kg (2,204.62 lb)
1 pound	0.45359237 kg

Material densities

Density is the most important variable in any weight calculation, and it varies. We use a representative average and display the typical range in the calculator's tooltip. Ranges are taken from quarry-published spec sheets across multiple regions of the US, then averaged. They are aligned with values commonly cited in landscaping and civil-engineering practice.

Material	Average lb/yd³	Range lb/yd³	Typical depth (in)
Pea Gravel (3/8")	2,450	2,400–2,500	2–3
Crushed Stone #57	2,750	2,700–2,800	4–6
Crushed Stone #8	2,700	2,650–2,750	2–4
Crushed Stone #4	2,650	2,600–2,700	4–8
River Rock (1"–3")	2,550	2,500–2,600	3–4
Decomposed Granite	2,550	2,500–2,600	2–3
Crushed Limestone	2,700	2,650–2,750	4–6
CA6 / 21AA / Class 5	2,650	2,600–2,700	4–6
ABC / Crusher Run	2,700	2,650–2,750	4–6
Recycled Concrete	2,650	2,600–2,700	4–6
Lava Rock	1,500	1,400–1,600	2–3
Concrete Sand	2,700	2,600–2,800	1–2

Note

These values assume dry, settled bulk weight. Wet aggregate weighs 5–10% more. Loose aggregate weighs 10–15% less. Your supplier's scale is the source of truth on delivery day.

Buffer / waste factor

The calculator's default buffer is 10%. This single buffer covers compaction, spillage, irregular edges, and small measurement errors — the standard practice across residential aggregate ordering. The buffer is applied to both the volume and weight outputs symmetrically. You can adjust it from 0 to 25% using the slider on any calculator page.

Limits and caveats

The calculator is not a structural-engineering tool. For bridges, highways, or load-rated structures, follow your engineer's spec.
Cost figures are rough. The default $50/ton and $65/yd³ are placeholders. Always replace them with a quote from your local supplier.
Density ranges are typical, not absolute. Crushed stone from a high-density basalt quarry can run 5–8% heavier than the limestone average we use.
Concrete-mix calculations follow nominal volumetric mix design with a standard 1.54 dry-volume factor. For structural concrete, follow ACI guidance and your engineer.

References & standards

The density figures used by this calculator are cross-checked against the following public sources. Where ranges differ, we use the midpoint and surface the full range in the material-picker tooltip.

ASTM D2940 / D448 — Standard Specification for Graded Aggregate Material (defines #57, #8, #4, etc. size grades used in the U.S. crushed-stone family).
USGS Mineral Commodity Summaries — Crushed Stone & Construction Sand and Gravel (annual). Industry-wide average densities and production data.
Vulcan Materials, Martin Marietta, and Lehigh Hanson product spec sheets — major U.S. quarry chains publishing density and grade data per product.
UK MOT Type 1 / DOT specification — for the metric calculator's sub-base material defaults.
ACI 211.1 — Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete — for the concrete-mix calculator's volumetric design factor and water-cement ratios.

Frequently asked questions

If you spot an error in any of the values above, please contact us — we update the methodology when better data is available.