# Engine Displacement Calculator

> Computes engine displacement from bore, stroke and cylinder count (V = π/4 × bore² × stroke × cylinders) in cc, litres and cubic inches, plus the per-cylinder volume and bore/stroke ratio.

- Calculator id: `engine-displacement` · Category: Engineering & Automotive (`engineering`) · Tool name: `calculate_engine_displacement`
- Canonical page: https://tttkmbb.com/engineering/engine-displacement · This document: https://tttkmbb.com/engineering/engine-displacement.md · JSON definition: https://tttkmbb.com/engineering/engine-displacement.json

## Purpose

Computes engine displacement from bore, stroke and cylinder count (V = π/4 × bore² × stroke × cylinders) in cc, litres and cubic inches, plus the per-cylinder volume and bore/stroke ratio.

**Use when:** You know an engine's bore and stroke and need its displacement, or want to check the effect of overboring or a stroker crank.

**Do not use when:** You need the compression ratio (use compression-ratio) or a rotary/Wankel engine (displacement is defined differently).

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `bore_mm` | number | mm | required | Cylinder bore diameter in millimetres (inches × 25.4). (> 0, max 1000) |
| `stroke_mm` | number | mm | required | Piston stroke in millimetres (inches × 25.4). (> 0, max 1000) |
| `cylinders` | integer |  | optional, default 4 | Number of cylinders. (min 1, max 32) |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `cylinder_volume_cc` | number | cc | π/4 × bore² × stroke for one cylinder (swept volume). |
| `displacement_cc` | number | cc | Total swept volume in cubic centimetres. |
| `displacement_l` | number | L | Displacement in litres. |
| `displacement_cubic_in` | number | cu in | Displacement in cubic inches (1 cu in = 16.387064 cc). |
| `bore_stroke_ratio` | number |  | bore_mm / stroke_mm. |
| `engine_geometry` | string |  | Oversquare (bore > stroke), square, or undersquare (stroke > bore). |

## Formula

`cylinder_volume_cc = π / 4 × (bore_mm / 10)² × (stroke_mm / 10); displacement_cc = cylinder_volume_cc × cylinders; displacement_l = displacement_cc / 1000; displacement_cubic_in = displacement_cc / 16.387064`

## Data Sources

- Wikipedia – Engine displacement — https://en.wikipedia.org/wiki/Engine_displacement (reference, retrieved 2026-09-24)
- NIST Special Publication 811 – Guide for the Use of the SI, Appendix B (conversion factors) — https://www.nist.gov/pml/special-publication-811 (standard, 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/engine-displacement?bore_mm=…&stroke_mm=…`
- `POST https://tttkmbb.com/api/v1/calculate/engine-displacement` 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/engine-displacement · OpenAPI operationId `calculate_engine_displacement` 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": "engine-displacement", "inputs": {…}}`

## Example

- 86 mm × 86 mm, 4 cylinders: inputs `{"bore_mm":86,"stroke_mm":86,"cylinders":4}` → `{"cylinder_volume_cc":499.56,"displacement_cc":1998.2,"displacement_l":1.998,"displacement_cubic_in":121.94,"bore_stroke_ratio":1,"engine_geometry":"Square (bore = stroke)"}`
- Chevrolet 350: 4.00 in × 3.48 in, 8 cylinders: inputs `{"bore_mm":101.6,"stroke_mm":88.392,"cylinders":8}` → `{"displacement_cc":5733,"displacement_l":5.733,"displacement_cubic_in":349.85,"engine_geometry":"Oversquare (bore > stroke)"}`

```
GET https://tttkmbb.com/api/v1/calculate/engine-displacement?bore_mm=86&stroke_mm=86&cylinders=4
```

## Limitations

You need the compression ratio (use compression-ratio) or a rotary/Wankel engine (displacement is defined differently). All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Why is a '2.0 L' engine not exactly 2000 cc?**

Marketing names round the swept volume; the geometric displacement is often a few cc off (1,998 cc here) and tax classes use the exact figure.

**Does displacement include the combustion chamber?**

No. Displacement is the swept volume between top and bottom dead centre only; the chamber volume enters the compression ratio instead.

## Related

- [Compression Ratio Calculator](https://tttkmbb.com/engineering/compression-ratio.md) — Static compression ratio from the same bore and stroke.
- [Cylinder Calculator](https://tttkmbb.com/geometry/cylinder.md) — Volume of a cylinder in general.
- [Horsepower, Torque and RPM Calculator](https://tttkmbb.com/engineering/horsepower-torque-rpm.md) — Power and torque relation for the engine.