# US gallons to Imperial gallons (gal (US) to gal (UK))

> Convert US gallons to imperial gallons: 1 gal (US) = 0.832674 gal (UK). Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

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

## Formula

- `1 gal (US) = 0.832674 gal (UK)`
- `imperial gallons = US gallons × 0.8326741846`
- Reverse: `US gallons = imperial gallons × 1.200949926`

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) = 4.16337 gal (UK)
- 12.5 gal (US) = 10.4084 gal (UK)
- 100 gal (US) = 83.2674 gal (UK)

## Conversion table

| US gallons (gal (US)) | Imperial gallons (gal (UK)) |
| --- | --- |
| 1 | 0.832674 |
| 2 | 1.66535 |
| 3 | 2.49802 |
| 4 | 3.3307 |
| 5 | 4.16337 |
| 6 | 4.99605 |
| 7 | 5.82872 |
| 8 | 6.66139 |
| 9 | 7.49407 |
| 10 | 8.32674 |
| 15 | 12.4901 |
| 20 | 16.6535 |
| 25 | 20.8169 |
| 30 | 24.9802 |
| 40 | 33.307 |
| 50 | 41.6337 |
| 75 | 62.4506 |
| 100 | 83.2674 |
| 200 | 166.535 |
| 250 | 208.169 |
| 500 | 416.337 |
| 1000 | 832.674 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=gal_us&to_unit=gal_uk` → 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":"gal_uk"}`
- 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 imperial gallons are in one gallon?**

1 gal (US) = 0.832674 gal (UK). 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 imperial gallons?**

Multiply the value in US gallons by 0.8326741846: imperial gallons = US gallons × 0.8326741846. For example, 5 gal (US) = 4.16337 gal (UK).

**How do I convert imperial gallons back to US gallons?**

Multiply by the inverse factor 1.200949926 (US gallons = imperial gallons × 1.200949926), or use the imperial gallons-to-US gallons page.

## Related conversions

- [Imperial gallons to US gallons](https://tttkmbb.com/conversion/imperial-gallons-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)