Every calculator on this site runs the same shared math library — one set of formulas, densities, and yields — so a guide and a calculator can never disagree. This page documents exactly what that math is, where the reference numbers come from, and how we keep them honest.
In short: volume is length × width × depth in feet, divided by 27. Densities are representative published ranges, not lab measurements. Costs are planning ballparks — always confirm with your supplier.
The core formula is the same across every calculator on this site:
Measurements entered in other units are converted to feet first, using these factors (each number below is the number of feet in one unit):
| Unit | Feet per unit |
|---|---|
| feet (ft) | 1 |
| inches (in) | 0.08333333333333333 |
| yards (yd) | 3 |
| centimeters (cm) | 0.0328084 |
| meters (m) | 3.28084 |
Cubic yards stay the primary result throughout the site; the metric equivalent shown alongside is 1 yd³ = 0.764554857984 m³.
For non-rectangular areas, the shape formulas below produce the plan-view area in square feet; multiplying by depth in feet gives cubic feet, and dividing by 27 gives cubic yards:
| Shape | You enter | Area formula |
|---|---|---|
| Rectangle | length × width | Area = length × width (square feet) |
| Circle | diameter | Area = π × (diameter ÷ 2)² (square feet) |
| Triangle | base × height | Area = base × height ÷ 2 (square feet) |
Calculators on this site apply a default 10% overage to the exact measured volume — the industry-standard planning buffer for ordering bulk material. It exists because real projects are never as tidy as a formula: soil compacts and settles, trucks spill, subgrades are uneven, and a little material is always wasted on site.
The pre-overage figure is your true measured quantity, and the overage figure is what we recommend ordering. Ordering exactly the measured amount is the most common cause of a second delivery — which usually costs more than the extra material would have.
Weight-per-cubic-yard figures are the one place where honesty requires a caveat. Density varies with moisture, compaction, and the exact product — a yard of wet sand is meaningfully heavier than a yard of dry sand. So our values are typical published loose bulk densities — ASTM C33 / industry supplier spec-sheet ranges; representative, not lab precision. They are defaults designed to give a realistic planning estimate, and each calculator's dropdown lists the material-type variants below. Tons are derived directly from the same figures (lbs ÷ 2,000), so the converters and the tables can never disagree.
| Material | Material type | lbs / yd³ | tons / yd³ |
|---|---|---|---|
| Concrete | Ready-mix concrete (default) | 4,050 | 2.02 |
| Gravel | Crushed stone (typical) (default) | 2,800 | 1.40 |
| Pea gravel | 2,700 | 1.35 | |
| River rock | 2,900 | 1.45 | |
| Crushed concrete (RCA) | 2,900 | 1.45 | |
| Decomposed granite | 2,650 | 1.32 | |
| Fill dirt | Screened fill (typical) (default) | 2,200 | 1.10 |
| Sandy soil | 2,400 | 1.20 | |
| Clay soil | 2,500 | 1.25 | |
| Topsoil | Screened topsoil (typical) (default) | 2,400 | 1.20 |
| Enriched garden soil | 2,200 | 1.10 | |
| Heavy clay topsoil | 2,600 | 1.30 | |
| Mulch | Bark / hardwood mulch (typical) (default) | 800 | 0.40 |
| Cedar mulch | 600 | 0.30 | |
| Pine bark mulch | 700 | 0.35 | |
| Bulk compost | 1,000 | 0.50 | |
| Sand | Mason / concrete sand (typical) (default) | 2,700 | 1.35 |
| Coarse fill sand | 2,800 | 1.40 | |
| Paver / joint sand | 2,700 | 1.35 | |
| Wet sand | 3,100 | 1.55 | |
| Rock | Mixed landscape rock (typical) (default) | 4,500 | 2.25 |
| River rock | 4,700 | 2.35 | |
| Limestone / flagstone | 4,800 | 2.40 | |
| Lava rock (lightweight) | 1,500 | 0.75 | |
| Garden soil | Garden soil (default) | 2,400 | 1.20 |
| Hot-mix asphalt | Hot-mix asphalt (typical) (default) | 3,915 | 1.96 |
| Warm-mix asphalt | 3,800 | 1.90 | |
| Reclaimed asphalt — millings | 3,300 | 1.65 |
These are representative ranges for planning. For weight-sensitive decisions (truck load limits, structural loads), use your supplier's product-specific spec sheet.
Bag counts come from manufacturer published yields — the coverage figures printed on the bag — not from our own estimates. The calculators use these bags-per-cubic-yard figures:
Real yield varies with mixing method and conditions, so bag counts are estimates. And a useful rule of thumb: for concrete, ready-mix delivery usually beats bag-mixing on cost once the order passes about 1–2 cubic yards.
Where the site shows cost estimates, they are planning ballparks, not quotes. Material prices vary widely by region, supplier, season, delivery distance, and order size. Use the estimates to budget and to compare suppliers on equal footing — then confirm the real number with your supplier before committing. See our cubic yard cost guide for how to read a quote and which questions to ask.
Because all calculators and reference tables read from one shared calculation library, a fix in one place fixes it everywhere. Content is reviewed against the calculator math before publication, and our editorial policy describes the research and review process in full.
If you find an error, report it via our contact page with the page name, the numbers you entered, and what looks wrong. Verified corrections are applied and dated — the page's last-modified date reflects when it was fixed.
Related: the data sources page publishes the full density, bag-yield, and conversion tables, the printable cheat sheet condenses them to one page, and the material guides and editorial policy describe the research process.
Straight answers, no fluff. Then run your own numbers above.
They are typical published loose bulk densities — ASTM C33 / industry supplier spec-sheet ranges — representative, not lab precision. Actual density varies with moisture, compaction, and the specific product, so confirm weight-sensitive numbers (like dump-truck load limits) with your supplier.
A 10% planning buffer is the industry-standard convention for ordering bulk material. It covers compaction and settling, spillage, uneven subgrade, and ordinary waste. You can treat the pre-overage number as your exact measured quantity.
They are based on manufacturer published yields for standard bag sizes (e.g., an 80 lb bag yields about 0.6 cu ft). Real yield varies with mixing, so bag counts are estimates, not guarantees — ready-mix is usually the better buy past about 1–2 cubic yards.
Suppliers quote specific products with their own density specs, moisture content, and yield factors, which legitimately differ from our representative figures. Use our calculators to estimate and compare, then confirm final quantities with the supplier before ordering.
Use the contact page (/contact/) with the calculator or page name, the numbers you entered, and what you believe is wrong. Every report is checked against the shared calculation library, and published corrections are dated.