Gallons to Imperial Gallons Converter - Convert gal (US) to gal (Imp) Instantly
Convert US gallons (gal) to Imperial gallons (UK gal) quickly and accurately with this easy-to-use volume converter. Ideal for fuel planning, brewing, aquariums, beverage packaging, logistics, and engineering tasks that require precise conversions between US and UK gallon standards.
Note: This tool converts US liquid gallons to Imperial (UK) gallons. If you need US gal ↔ liters or UK gal ↔ liters, use the dedicated tools for those conversions.
About Gallons (US) to Imperial Gallons Conversion
US gallons (gal) and Imperial gallons (UK gal) both measure liquid volume, but they are not interchangeable. A US gallon is legally defined as 3.785411784 liters, while an Imperial (UK) gallon is defined as 4.54609 liters. Because the UK gallon is larger, any number of US gallons will convert to fewer Imperial gallons. This converter applies the exact ratio through liters so your results are accurate, auditable, and consistent with engineering and regulatory references.
Why go via liters? The liter is the SI reference, and both gallon definitions are tied to liters. Using the exact liter constants avoids rounding drift, keeps your documentation precise, and prevents confusion when working across US, UK, and metric standards.
Conversion Formula
Use the exact liter-based ratio:
UK gal = US gal × (3.785411784 ÷ 4.54609) ≈ US gal × 0.832674Example:
10 US gal = 10 × (3.785411784 ÷ 4.54609) = 8.32674 UK gal
To reverse the calculation:
US gal = UK gal ÷ (3.785411784 ÷ 4.54609) = UK gal × 1.200949.
US vs Imperial Gallons
The US gallon is common in the United States for fuel, beverages, and various liquid products. The Imperial gallon is primarily referenced in the United Kingdom and in certain maritime and historical contexts. The UK gallon’s larger size (4.54609 L vs 3.785411784 L) creates a difference of about 20%. Always confirm which gallon your source uses before converting values, especially in recipes, dosing, tank sizing, and compliance reports.
Why Convert US gal to UK gal?
- ⛽ Fuel comparisons: Translate US vehicle or tank specs into UK references.
- 🍺 Brewing & distilling: Align US recipes or vessel volumes with UK gallon documentation.
- 🐠 Aquariums & aquaculture: Match dosing schedules across unit systems.
- 🥤 Beverage packaging: Prepare international labels and production notes.
- 📦 Logistics & compliance: Convert legacy or regional specs for audits and standardized reporting.
Common Conversions
- 1 US gal = 0.83267 UK gal
- 2 US gal = 1.66535 UK gal
- 5 US gal = 4.16337 UK gal
- 10 US gal = 8.32674 UK gal
- 20 US gal = 16.65348 UK gal
- 50 US gal = 41.63371 UK gal
- 100 US gal = 83.26742 UK gal
What is a US Gallon?
A US gallon is a customary unit of liquid volume used mainly in the United States. It is defined as 231 cubic inches, exactly 3.785411784 liters. You’ll see it in fuel sales, beverage jugs, and many consumer products.
What is an Imperial (UK) Gallon?
An Imperial gallon is a UK unit of liquid volume defined as exactly 4.54609 liters (160 Imperial fluid ounces). It remains a reference in brewing, maritime contexts, and historical documentation even though modern UK retail largely uses liters for labeling.
Step-by-Step: Converting US gal to UK gal
- Write down your volume in US gallons.
- Multiply by 3.785411784 ÷ 4.54609 (≈ 0.832674).
- Express the result in UK gal (Imperial gallons).
Example walkthrough:
Input: 7.5 US gal
Multiply: 7.5 × (3.785411784 ÷ 4.54609) = 6.24506
Output: 6.24506 UK galPrecision, Rounding & Significant Figures
Five decimal places are ample for most practical applications. In technical contexts, match your reporting precision to sensors and standards. Keep significant figures consistent across chained calculations to minimize rounding error.
Use Cases of US gal → UK gal
- 🚗 Converting US automotive specs for UK-oriented comparisons
- 🍻 Translating US brew volumes into Imperial gallon references
- 🐟 Aligning aquaculture dosing with regional unit requirements
- 🥫 Preparing packaging and labels for UK markets
- 🧪 Adapting lab or SOP documentation that mixes US and UK units
Quick Reference Table
| US Gallons (gal) | Imperial Gallons (UK gal) |
|---|---|
| 1 | 0.83267 |
| 2 | 1.66535 |
| 5 | 4.16337 |
| 10 | 8.32674 |
| 20 | 16.65348 |
| 50 | 41.63371 |
Frequently Asked Questions
How do you convert US gallons to Imperial gallons?
Multiply US gallons by the exact ratio 3.785411784 ÷ 4.54609. In other words: UK gal = US gal × (3.785411784 / 4.54609) ≈ US gal × 0.832674.
How many Imperial gallons are in 1 US gallon?
1 US gallon ≈ 0.83267 Imperial gallons. The ratio comes from 3.785411784 L per US gal divided by 4.54609 L per UK gal.
Why are US and Imperial gallons different?
They originate from different historical definitions. A US gallon is exactly 3.785411784 liters, while an Imperial (UK) gallon is exactly 4.54609 liters—about 20% larger.
How do I convert Imperial gallons back to US gallons?
Divide by the same ratio: US gal = UK gal ÷ (3.785411784 / 4.54609) = UK gal × 1.200949. Alternatively convert both via liters if you prefer.
Is this tool for liquid gallons?
Yes, this tool is for liquid volume. It converts US liquid gallons to Imperial (UK) gallons using the exact definitions in liters.
Tips for Working Across Gallon Systems
- Always state which gallon you mean—US or Imperial—next to the number.
- For reproducibility, include the exact liter factors (3.785411784 and 4.54609) in technical notes.
- For small quantities, convert to liters or milliliters to simplify measurement and dosing.