Gravel Calculators
Methodology
This page documents exactly how the calculators on this site work: the formulas, the density figures held in the code, how units and rounding are handled, and how the tools are tested. Found a mistake? Report an error and it will be checked and fixed.
How the calculations work
Every quantity calculator on this site uses the same core formulas:
- Area: rectangle = length × width; circle = π × radius²; triangle = ½ × base × height.
- Volume: cubic feet = area (ft²) × depth (ft). Depth entered in inches is divided by 12; centimeters divided by 30.48; meters multiplied by 3.28084.
- Cubic yards: cubic feet ÷ 27.
- Cubic meters: cubic feet × 0.0283168.
- Weight: tons (US short) = cubic yards × density (tons per yd³); pounds = tons × 2,000; kilograms = cubic meters × density (kg/m³).
- Bags: cubic feet ÷ 0.5 (the common retail bag size).
- Cost: tons × price per ton, or cubic yards × price per cubic yard — using a rate you enter, never a built-in price.
- Concrete mixes: the target volume is multiplied by 1.54 (the dry-volume factor) and then divided by the total ratio parts; cement bags = cement dry volume in ft³ (a 94-lb bag occupies about 1 ft³).
- Post holes: each hole's gravel = π × radius² × layer depth, in cubic inches, converted to cubic feet (÷ 1,728).
- : tank length × width × substrate depth in cubic inches; pounds = cubic feet × density in lb/ft³.
Units and rounding
You can enter dimensions in feet or meters and depth in inches, feet, centimeters, or meters; everything is converted to feet internally. Results are shown in cubic yards, cubic feet, cubic meters, US tons, pounds, kilograms, and bags. Displayed figures are rounded to 2 decimals (1 decimal above 100, whole numbers above 1,000) for readability — the underlying math is not rounded, so copying results into a spreadsheet may differ by a rounding step.
Density assumptions
The figures below are the actual values held in the site's code
(assets/js/materials.js). They are typical averages for loose,
dry material — they are not supplier specifications, and they vary with
gradation, moisture, and compaction. Every calculator displays the figure it is using
alongside the result.
| Material | kg/m³ | lb/ft³ | tons/yd³ |
|---|---|---|---|
| Gravel (loose, dry) | 1,680 | 105 | 1.42 |
| Pea gravel | 1,760 | 110 | 1.49 |
| Crushed stone | 1,700 | 106 | 1.43 |
| Crusher run / road base | 1,900 | 119 | 1.60 |
| Sand (dry) | 1,600 | 100 | 1.35 |
| #57 stone (¾", washed) | 1,600 | 100 | 1.35 |
| #67 stone (¾" minus) | 1,620 | 101 | 1.37 |
| #4 stone (1½–2½") | 1,500 | 94 | 1.27 |
| #1 stone (2–4") | 1,450 | 91 | 1.23 |
Sources
The density figures above are typical industry averages for loose, dry aggregate, drawn from the commonly published ranges you will find across supplier and reference material (gravel generally runs 1.4–1.7 tons per cubic yard depending on type and compaction). No single supplier supplied or endorsed these figures, and no specific source is cited as authoritative — that is exactly why every calculator shows its density and recommends confirming final quantities with your own supplier, whose sieve sheet and scale beat any table.
How the calculators are tested
Before publication, every calculator's formulas are checked against hand calculations, and the site includes an automated script that re-computes the same math independently. Examples of hand-verified cases that were actually run:
- 20 × 10 ft at 3 in of gravel (1,680 kg/m³): 50 ft³ = 1.85 yd³ = 2.62 tons — matches the tool.
- 12 × 50 ft driveway, 4-in crusher-run base plus 3-in #57 top: 11.9 + 7.5 = 19.4 tons; at $40/$45 per ton the cost tool returns about $813 — matches the tool and the worked examples.
- Circle, 12 ft diameter at 4 in of #57: 1.4 yd³ = 1.88 tons — matches the tool.
- Metric: 5 × 3 m at 10 cm of pea gravel: 1.96 yd³ ≈ 2.9 tons — matches the tool.
- Fence posts: 24 posts, 12-in holes with a 6-in gravel layer: 0.39 ft³ per post, 19 bags — matches the tool.
- Concrete, 1 yd³ of 1:2:3 with 1.54 dry-volume factor: 41.6 ft³ dry volume ÷ 6 parts = 6.9 ft³ cement = 7 ninety-four-pound bags — matches the tool.
- Edge cases: zero, negative, and implausibly large inputs are rejected with an error message rather than producing a result.
Quality standards
- Every calculator shows the formula and the density figure it used — no hidden math.
- All tools read densities from one shared data file, so figures cannot drift between pages.
- Every page labels results as estimates and names the real-world factors (compaction, moisture, supplier rounding) that change actual orders.
- No invented statistics, credentials, or sources anywhere on the site.
Review cadence
Pages and calculators are reviewed at least every 6 months, and additionally whenever an error is reported. Each calculator page shows the date of its last review. Corrections are logged on the report-an-error page.
Found a problem this page didn't catch? Report an error.
Last reviewed: by ianwelkins