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

> Convert imperial gallons to US gallons: 1 gal (UK) = 1.20095 gal (US). Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

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

## Formula

- `1 gal (UK) = 1.20095 gal (US)`
- `US gallons = imperial gallons × 1.200949926`
- Reverse: `imperial gallons = US gallons × 0.8326741846`

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 (UK) = 6.00475 gal (US)
- 12.5 gal (UK) = 15.0119 gal (US)
- 100 gal (UK) = 120.095 gal (US)

## Conversion table

| Imperial gallons (gal (UK)) | US gallons (gal (US)) |
| --- | --- |
| 1 | 1.20095 |
| 2 | 2.4019 |
| 3 | 3.60285 |
| 4 | 4.8038 |
| 5 | 6.00475 |
| 6 | 7.2057 |
| 7 | 8.40665 |
| 8 | 9.6076 |
| 9 | 10.8085 |
| 10 | 12.0095 |
| 15 | 18.0142 |
| 20 | 24.019 |
| 25 | 30.0237 |
| 30 | 36.0285 |
| 40 | 48.038 |
| 50 | 60.0475 |
| 75 | 90.0712 |
| 100 | 120.095 |
| 200 | 240.19 |
| 250 | 300.237 |
| 500 | 600.475 |
| 1000 | 1200.95 |

## API

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

1 gal (UK) = 1.20095 gal (US). 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 imperial gallons to US gallons?**

Multiply the value in imperial gallons by 1.200949926: US gallons = imperial gallons × 1.200949926. For example, 5 gal (UK) = 6.00475 gal (US).

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

Multiply by the inverse factor 0.8326741846 (imperial gallons = US gallons × 0.8326741846), or use the US gallons-to-imperial gallons page.

## Related conversions

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