# Steel Weight Calculator

> Computes the cross-section area, weight per metre and total weight of round, square, hexagonal and flat bars, plates and sheets, round tubes or pipes and rectangular tubes from their dimensions in millimetres, the length, quantity and material density (carbon steel 7,850 kg/m³, stainless 304, aluminium, copper, brass, titanium or a custom value).

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

## Purpose

Computes the cross-section area, weight per metre and total weight of round, square, hexagonal and flat bars, plates and sheets, round tubes or pipes and rectangular tubes from their dimensions in millimetres, the length, quantity and material density (carbon steel 7,850 kg/m³, stainless 304, aluminium, copper, brass, titanium or a custom value).

**Use when:** You need the weight of metal stock for ordering, pricing by the kilogram, load calculations or shipping.

**Do not use when:** The section is a rolled profile such as an I-beam, channel or angle (use the published kg/m from the section tables), or the material is not metal (use density-mass-volume with the material's density).

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `shape` | enum: round_bar \| square_bar \| flat_bar_or_plate \| sheet \| round_tube_or_pipe \| rectangular_tube \| hexagon_bar |  | optional, default "round_bar" | Cross-section type; the label lists which dimensions it uses. |
| `diameter_mm` | number | mm | optional | Diameter of a round bar or the outside diameter of a tube/pipe, in millimetres. (> 0, max 5000) |
| `width_mm` | number | mm | optional | Width of a flat bar, plate, sheet or rectangular tube; side of a square bar; across-flats size of a hexagon bar (mm). (> 0, max 10000) |
| `height_mm` | number | mm | optional | Height (second outside dimension) of a rectangular tube, in millimetres. (> 0, max 10000) |
| `thickness_mm` | number | mm | optional | Thickness of a flat bar, plate or sheet, in millimetres. (> 0, max 1000) |
| `wall_thickness_mm` | number | mm | optional | Wall thickness of a round or rectangular tube, in millimetres. (> 0, max 500) |
| `length_m` | number | m | required | Length of one piece in metres (for plate and sheet, the second plan dimension). (> 0, max 1000) |
| `quantity` | integer |  | optional, default 1 | Number of identical pieces. (min 1, max 100000) |
| `material` | enum: carbon_steel \| stainless_304 \| aluminium \| copper \| brass \| titanium |  | optional, default "carbon_steel" | Material preset for the density; density_kg_m3 overrides it. |
| `density_kg_m3` | number | kg/m³ | optional | Optional density in kg/m³ that overrides the material preset (e.g. 7,200 for cast iron, 11,340 for lead). (> 0, max 25000) |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `cross_section_area_mm2` | number | mm² | Area of the metal cross-section. |
| `weight_per_metre_kg` | number | kg/m | area_m² × density. |
| `weight_per_foot_lb` | number | lb/ft | Same linear weight in pounds per foot. |
| `total_weight_kg` | number | kg | weight_per_metre × length_m × quantity. |
| `total_weight_lb` | number | lb | Total weight in pounds (1 kg = 2.20462 lb). |
| `volume_m3` | number | m³ | area × length × quantity. |
| `density_used_kg_m3` | number | kg/m³ | Density applied. |

## Formula

`area: round π/4·d²; square w²; flat/plate/sheet w × t; round tube π/4·(D² − (D − 2t)²); rectangular tube w × h − (w − 2t)(h − 2t); hexagon (√3/2)·AF². weight_per_metre = area_mm² × 10⁻⁶ × density; total = weight_per_metre × length_m × quantity.`

Densities are nominal: carbon steel 7,850 kg/m³ (the value used in structural steel tables, e.g. 20 mm round bar = 2.466 kg/m), stainless 304 about 7,930 (published values 7,900–8,000), aluminium alloys 2,700, copper 8,960, brass 8,400–8,700 (8,500 used), commercially pure titanium 4,500 (Ti-6Al-4V 4,430). Nominal dimensions are used; rolling tolerances change real weights by a few percent.

## Data Sources

- Wikipedia – Steel (density) — https://en.wikipedia.org/wiki/Steel (reference, retrieved 2026-09-24)
- Engineering ToolBox – Metals and alloys: densities — https://www.engineeringtoolbox.com/metal-alloys-densities-d_50.html (reference, retrieved 2026-09-24)
- Wikipedia – Density — https://en.wikipedia.org/wiki/Density (reference, retrieved 2026-09-24)

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/steel-weight?length_m=…`
- `POST https://tttkmbb.com/api/v1/calculate/steel-weight` 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/steel-weight · OpenAPI operationId `calculate_steel_weight` 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": "steel-weight", "inputs": {…}}`

## Example

- 20 mm round bar, 6 m, carbon steel: inputs `{"shape":"round_bar","diameter_mm":20,"length_m":6,"quantity":1,"material":"carbon_steel"}` → `{"cross_section_area_mm2":314.16,"weight_per_metre_kg":2.466,"weight_per_foot_lb":1.657,"total_weight_kg":14.8,"total_weight_lb":32.62,"volume_m3":0.00188,"density_used_kg_m3":7850}`
- Steel plate 1000 × 2000 × 10 mm: inputs `{"shape":"flat_bar_or_plate","width_mm":1000,"thickness_mm":10,"length_m":2}` → `{"cross_section_area_mm2":10000,"weight_per_metre_kg":78.5,"total_weight_kg":157,"total_weight_lb":346.13}`

```
GET https://tttkmbb.com/api/v1/calculate/steel-weight?shape=round_bar&diameter_mm=20&length_m=6&quantity=1&material=carbon_steel
```

## Limitations

The section is a rolled profile such as an I-beam, channel or angle (use the published kg/m from the section tables), or the material is not metal (use density-mass-volume with the material's density). Densities are nominal: carbon steel 7,850 kg/m³ (the value used in structural steel tables, e.g. 20 mm round bar = 2.466 kg/m), stainless 304 about 7,930 (published values 7,900–8,000), aluminium alloys 2,700, copper 8,960, brass 8,400–8,700 (8,500 used), commercially pure titanium 4,500 (Ti-6Al-4V 4,430). Nominal dimensions are used; rolling tolerances change real weights by a few percent. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**How do I enter a plate?**

Use flat_bar_or_plate with width_mm and thickness_mm as the cross-section and the plate's other plan dimension as length_m (a 1,000 × 2,000 × 10 mm plate: width 1000, thickness 10, length 2).

**Why does my pipe table show a different kg/m?**

Pipe tables use the nominal wall and a density of 7,850 kg/m³ but round to the standard's convention; a 48.3 × 3.2 mm tube computes to 3.56 kg/m, matching the table. Larger differences come from a different outside diameter or wall.

**Can I use this for cast iron or lead?**

Yes: leave material at any preset and enter density_kg_m3 (cast iron ≈ 7,200, lead 11,340, zinc 7,140).

## Related

- [Density Calculator](https://tttkmbb.com/physics/density-mass-volume.md) — Mass from volume and density for any material.
- [Mass / Weight Converter](https://tttkmbb.com/conversion/mass.md) — Convert the weight to other mass units.
- [Rebar Calculator](https://tttkmbb.com/construction/rebar.md) — Reinforcing bar weight for a slab grid.