# US gallons to Cubic meters (gal (US) to m³)

> Convert US gallons to cubic meters: 1 gal (US) = 0.00378541 m³. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

- Page id: `gallons-to-cubic-meters` · Quantity: Volume (`volume`, base unit L) · Tool: `convert_units`
- Canonical page: https://tttkmbb.com/conversion/gallons-to-cubic-meters · This document: https://tttkmbb.com/conversion/gallons-to-cubic-meters.md · JSON: https://tttkmbb.com/conversion/gallons-to-cubic-meters.json (add `?value=` for a result)

## Formula

- `1 gal (US) = 0.00378541 m³`
- `cubic meters = US gallons × 0.003785411784`
- Reverse: `US gallons = cubic meters × 264.1720524`

The factor follows from the SI definitions of both units (NIST SP 811); values below are rounded to 6 significant figures, the API returns up to 12.

## Worked examples

- 5 gal (US) = 0.0189271 m³
- 12.5 gal (US) = 0.0473176 m³
- 100 gal (US) = 0.378541 m³

## Conversion table

| US gallons (gal (US)) | Cubic meters (m³) |
| --- | --- |
| 1 | 0.00378541 |
| 2 | 0.00757082 |
| 3 | 0.0113562 |
| 4 | 0.0151416 |
| 5 | 0.0189271 |
| 6 | 0.0227125 |
| 7 | 0.0264979 |
| 8 | 0.0302833 |
| 9 | 0.0340687 |
| 10 | 0.0378541 |
| 15 | 0.0567812 |
| 20 | 0.0757082 |
| 25 | 0.0946353 |
| 30 | 0.113562 |
| 40 | 0.151416 |
| 50 | 0.189271 |
| 75 | 0.283906 |
| 100 | 0.378541 |
| 200 | 0.757082 |
| 250 | 0.946353 |
| 500 | 1.89271 |
| 1000 | 3.78541 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=gal_us&to_unit=m3` → unified JSON envelope with `result.values.result`, `formula`, `factor`, `sources`, `freshness`
- MCP: server `https://tttkmbb.com/mcp`, tool `convert_units` with `{"value":5,"from_unit":"gal_us","to_unit":"m3"}`
- All volume units: https://tttkmbb.com/api/v1/units?quantity=volume · full converter: [Volume Converter](https://tttkmbb.com/conversion/volume.md)
- Authentication: none. Freshness: `static` (fixed conversion factors).

## FAQ

**How many cubic meters are in one gallon?**

1 gal (US) = 0.00378541 m³. The factor comes from the SI definitions of both units (NIST SP 811 / BIPM), so it is exact or correct to at least 10 significant figures.

**What is the formula to convert US gallons to cubic meters?**

Multiply the value in US gallons by 0.003785411784: cubic meters = US gallons × 0.003785411784. For example, 5 gal (US) = 0.0189271 m³.

**How do I convert cubic meters back to US gallons?**

Multiply by the inverse factor 264.1720524 (US gallons = cubic meters × 264.1720524), or use the cubic meters-to-US gallons page.

## Related conversions

- [Cubic meters to US gallons](https://tttkmbb.com/conversion/cubic-meters-to-gallons.md) (reverse)
- [Liters to US gallons](https://tttkmbb.com/conversion/liters-to-gallons.md)
- [US gallons to Liters](https://tttkmbb.com/conversion/gallons-to-liters.md)
- [Milliliters to US fluid ounces](https://tttkmbb.com/conversion/ml-to-fl-oz.md)
- [US fluid ounces to Milliliters](https://tttkmbb.com/conversion/fl-oz-to-ml.md)
- [Liters to Milliliters](https://tttkmbb.com/conversion/liters-to-ml.md)
- [Milliliters to Liters](https://tttkmbb.com/conversion/ml-to-liters.md)
- [US cups to Milliliters](https://tttkmbb.com/conversion/cups-to-ml.md)
- [Milliliters to US cups](https://tttkmbb.com/conversion/ml-to-cups.md)

## Data Sources

- NIST Special Publication 811 – Guide for the Use of the International System of Units (SI), Appendix B conversion factors — https://www.nist.gov/pml/special-publication-811 (standard, retrieved 2026-09-24)
- BIPM – The International System of Units (SI Brochure, 9th edition) — https://www.bipm.org/en/publications/si-brochure (standard, retrieved 2026-09-24)
- Wikipedia – Conversion of units — https://en.wikipedia.org/wiki/Conversion_of_units (reference, retrieved 2026-09-24)