# Gravel Calculator

> Computes the volume of loose aggregate needed to cover an area to a given depth and converts it to weight with a typical bulk density for gravel, crushed stone, sand, topsoil or mulch (or a custom density).

- Calculator id: `gravel` · Category: Construction & Home (`construction`) · Tool name: `estimate_gravel_volume`
- Canonical page: https://tttkmbb.com/construction/gravel · This document: https://tttkmbb.com/construction/gravel.md · JSON definition: https://tttkmbb.com/construction/gravel.json

## Purpose

Computes the volume of loose aggregate needed to cover an area to a given depth and converts it to weight with a typical bulk density for gravel, crushed stone, sand, topsoil or mulch (or a custom density).

**Use when:** You need to order gravel, crushed stone, sand, topsoil or bark mulch by volume (m³, yd³) or by weight (tonnes, US tons) for a driveway, path, bed or sub-base.

**Do not use when:** The material is concrete (use concrete-slab) or you need the density of a specific product: use the supplier's figure via material = custom and density_t_per_m3.

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `unit_system` | enum: metric \| imperial |  | optional, default "metric" | Unit system of the length inputs (metric: m / cm / mm; imperial: ft / in). Outputs are reported in both systems. |
| `length` | number | m or ft | optional | Length of the area (m or ft). Give length and width, or area. (> 0, max 10000) |
| `width` | number | m or ft | optional | Width of the area (m or ft). (> 0, max 10000) |
| `area` | number | m² or ft² | optional | Area to cover (m² or ft²); used instead of length × width when given. (> 0) |
| `depth` | number | cm or in | required | Depth of the layer in centimetres (metric) or inches (imperial). Typical: 5 cm / 2 in decorative gravel, 10–15 cm / 4–6 in driveway base, 7.5 cm / 3 in mulch. (> 0, max 500) |
| `material` | enum: gravel \| crushed_stone \| sand \| topsoil \| mulch \| custom |  | optional, default "gravel" | Selects a typical loose bulk density in tonnes per cubic metre. |
| `density_t_per_m3` | number | t/m³ | optional | Bulk density in tonnes per m³ (= kg/L); required for material = custom and overrides the preset otherwise. (> 0, max 10) |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `area_m2` | number | m² | Area covered. |
| `volume_m3` | number | m³ | area × depth. |
| `volume_cubic_yards` | number | yd³ | Same volume in cubic yards. |
| `volume_cubic_feet` | number | ft³ | Same volume in cubic feet. |
| `density_used_t_per_m3` | number | t/m³ | Bulk density applied. |
| `weight_tonnes` | number | t | volume_m3 × density (metric tonnes). |
| `weight_kg` | number | kg | Weight in kilograms. |
| `weight_us_tons` | number | US short tons | Weight in US short tons (1 t = 1.10231 short tons). |

## Formula

`area = length × width (or area); volume_m³ = area_m² × depth_m; yd³ = m³ / 0.764555; tonnes = m³ × density_t_per_m³; short tons = tonnes × 1.10231. Densities: gravel 1.6, crushed stone 1.6, sand 1.5, topsoil 1.2, mulch 0.4 t/m³.`

Loose bulk densities vary with moisture and grading (dry gravel ≈ 1.68 t/m³, dry sand ≈ 1.56 t/m³, loose earth ≈ 1.22 t/m³ per Engineering ToolBox); compacted sub-base settles by 10–20 %, so order extra for compacted layers.

## Data Sources

- Engineering ToolBox – Densities of dirt, mud, gravel and sand — https://www.engineeringtoolbox.com/dirt-mud-densities-d_1727.html (reference, retrieved 2026-09-23)
- Wikipedia – Bulk density — https://en.wikipedia.org/wiki/Bulk_density (reference, retrieved 2026-09-23)

Data freshness: `static`. Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output.

## API

- `GET https://tttkmbb.com/api/v1/calculate/gravel?depth=…`
- `POST https://tttkmbb.com/api/v1/calculate/gravel` with JSON body `{"inputs": {…}}`
- Response: unified envelope (`success`, `request`, `result.values`, `result.units`, `sources`, `freshness`, `timestamp`, `next_actions`, `links`); see https://tttkmbb.com/docs/response-format.md
- Schema: https://tttkmbb.com/api/v1/calculators/gravel · OpenAPI operationId `estimate_gravel_volume` in https://tttkmbb.com/openapi.json
- Authentication: none. Rate limit: fair use, see https://tttkmbb.com/docs/rate-limits.md.

## MCP

- Server: `https://tttkmbb.com/mcp` (Streamable HTTP, JSON-RPC 2.0, no auth)
- Tool:  `run_calculator` with `{"calculator_id": "gravel", "inputs": {…}}`

## Example

- 10 m × 5 m of gravel, 5 cm deep: inputs `{"unit_system":"metric","length":10,"width":5,"depth":5,"material":"gravel"}` → `{"area_m2":50,"volume_m3":2.5,"volume_cubic_yards":3.27,"volume_cubic_feet":88.29,"density_used_t_per_m3":1.6,"weight_tonnes":4,"weight_kg":4000,"weight_us_tons":4.409}`
- 20 ft × 10 ft of mulch, 3 in deep: inputs `{"unit_system":"imperial","length":20,"width":10,"depth":3,"material":"mulch"}` → `{"area_m2":18.58,"volume_cubic_feet":50,"volume_cubic_yards":1.852,"volume_m3":1.416,"weight_tonnes":0.566,"weight_us_tons":0.624}`

```
GET https://tttkmbb.com/api/v1/calculate/gravel?unit_system=metric&length=10&width=5&depth=5&material=gravel
```

## Limitations

The material is concrete (use concrete-slab) or you need the density of a specific product: use the supplier's figure via material = custom and density_t_per_m3. Loose bulk densities vary with moisture and grading (dry gravel ≈ 1.68 t/m³, dry sand ≈ 1.56 t/m³, loose earth ≈ 1.22 t/m³ per Engineering ToolBox); compacted sub-base settles by 10–20 %, so order extra for compacted layers. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Do suppliers sell by weight or volume?**

Bulk aggregates are usually sold by the tonne or by the cubic yard/metre; a bulk bag holds about 0.5 m³ (≈ 0.8 t of gravel). Use whichever figure matches the supplier's price list.

**How much extra should I order?**

Add 5–10 % for uneven ground and spillage, and 10–20 % more for layers that will be compacted (road base, sub-base under paving).

## Related

- [Concrete Slab Calculator](https://tttkmbb.com/construction/concrete-slab.md) — Concrete poured on the sub-base.
- [Volume Converter](https://tttkmbb.com/conversion/volume.md) — Convert between m³, yd³ and litres.
- [Density Calculator](https://tttkmbb.com/physics/density-mass-volume.md) — Mass from volume and density for other materials.