Authoritative definitions of the International System of Units and SI prefixes.
Dedicated unit pair
Imperial gallons to US gallons
Convert imp gal to US gal instantly, then review the formula, assumptions, and rounding guidance.
VolumeInstant result
Decimals
Formula result = input × 4.54609 ÷ 3.785411784. 1 imp gal = 1.2009 US gal
Common examples
One value, several units
Litres4.5461 L
Millilitres4,546.09 mL
Cubic metres0.0045 m³
Cubic centimetres4,546.09 cm³
US gallons1.2009 US gal
US quarts4.8038 qt
US cups19.2152 cup
US fluid ounces153.7216 fl oz
Conversion table
| imp gal | US gal |
|---|---|
| 1 imp gal | 1.2009 US gal |
| 2 imp gal | 2.4019 US gal |
| 5 imp gal | 6.0047 US gal |
| 10 imp gal | 12.0095 US gal |
| 25 imp gal | 30.0237 US gal |
| 50 imp gal | 60.0475 US gal |
| 100 imp gal | 120.095 US gal |
Conversion chart
1 imp gal1.2009 US gal
5 imp gal6.0047 US gal
10 imp gal12.0095 US gal
25 imp gal30.0237 US gal
50 imp gal60.0475 US gal
Worked example
1 litre equals 1,000 millilitres.
Unit definition
Imperial gallons (imp gal) One imperial gallons equals 4.54609 litre.
Unit history
Imperial gallons is represented here using its modern SI definition or an internationally accepted relationship to an SI base unit.
Step by step
1. Parse the value, including fractions.
2. Convert imp gal to litre.
3. Convert the base value to US gal and apply your display precision.
Understand the result before using it
Imperial gallons to US gallons converts a value measured in Imperial gallons (imp gal) into the equivalent value in US gallons (US gal). The numerical value changes because the size and definition of the selected unit changes; the underlying quantity does not.
Calculated result
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.
Formula, assumptions, and example
Formula
result = input × 4.54609 ÷ 3.785411784
Assumptions
- Imperial gallons and US gallons represent the same volume quantity.
- The input is expressed in imp gal; the output is expressed in US gal.
- The unit definitions and conventional relationship shown on this page apply.
Worked example
1 imp gal = 1.2009499255 US gal. For another value, apply the same relationship and round only to the precision your source measurement supports.
When to use it
Good uses
- Read a imp gal measurement in a document that expects US gal.
- Compare a imperial gallons value with a value reported in us gallons.
- Check the imp gal-to-US gal arithmetic before copying the result into another calculation.
Limitations
Common mistakes to avoid
- US gallons and imperial gallons are different units; select the one your source actually uses.
- Round the output to a precision justified by the original measurement.
- Verify safety-critical, regulated, laboratory, and contractual conversions against the controlling standard.
Sources and further reading
These references explain the underlying standards or provide authoritative context. Your own contract, institution, clinician, product documentation, local code, or governing standard may be the controlling source.
Guidance on unit names, symbols, conversions, and numerical presentation.
Questions about this calculation
How do I convert Imperial gallons to US gallons?
result = input × 4.54609 ÷ 3.785411784 Using the displayed relationship, 1 imp gal equals 1.2009499255 US gal.
How many US gallons are in one Imperial gallons?
One Imperial gallons is 1.2009499255 US gallons. The displayed digits may be rounded.
Can I reverse the imp gal to US gal conversion?
Yes. Swap the source and target units in the converter. The reverse relationship converts US gal back to imp gal.
Is the Imperial gallons to US gallons result exact?
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.