21 Miles/Gallon (UK) to Gallon (US)/100mi
Quick answer
21 Miles/Gallon (UK) (mpg (UK)) equals
31.63984 gal/100mi
To convert 21 Miles/Gallon (UK)s to Gallon (US)/100mis, multiply by 664.4366303531. Therefore, 21 Miles/Gallon (UK) (mpg (UK)) equals 31.63984 Gallon (US)/100mi (gal/100mi).
Formula: gal/100mi = mpg (UK) × 664.4366303531. Calculation: 31.63984 gal/100mi. Reverse: mpg (UK) = gal/100mi × 664.4366303531.
Convert Miles/Gallon (UK) (mpg (UK)) to Gallon (US)/100mi (gal/100mi) online with our free unit converter. Calculated using formula: gal/100mi = mpg (UK) × 664.4366303531. Explore step-by-step conversion steps, mathematical formulas, and quick conversion reference tables below.
Worked example: converting Miles/Gallon (UK) to Gallon (US)/100mi
- Step 1 — start with the formula. gal/100mi = mpg (UK) × 664.4366303531
- Step 2 — substitute your figure. Apply the formula to 21 mpg (UK).
- Step 3 — read the result. 21 mpg (UK) = 31.63984 gal/100mi
- Step 4 — check it in reverse. mpg (UK) = gal/100mi × 664.4366303531 returns 21 mpg (UK), which matches the figure you started with.
Fuel Economy Converter
11 units available
21 mpg (UK) = 31.63984 gal/100mi
Formula:
gal/100mi = mpg (UK) × 664.4366303531With your value: 21 mpg (UK) = 31.63983954 gal/100mi
Other Miles/Gallon (UK) to Gallon (US)/100mi conversions
Miles/Gallon (UK) to Gallon (US)/100mi Conversion Table
| Miles/Gallon (UK) (mpg (UK)) | Gallon (US)/100mi (gal/100mi) |
|---|---|
| 0.5 | 1,328.873261 |
| 1 | 664.43663 |
| 2 | 332.218315 |
| 5 | 132.887326 |
| 10 | 66.443663 |
| 15 | 44.295775 |
| 20 | 33.221832 |
| 25 | 26.577465 |
| 50 | 13.288733 |
| 100 | 6.644366 |
| 250 | 2.657747 |
| 500 | 1.328873 |
| 1000 | 0.664437 |
Gallon (US)/100mi to Miles/Gallon (UK) Conversion Table
| Gallon (US)/100mi (gal/100mi) | Miles/Gallon (UK) (mpg (UK)) |
|---|---|
| 0.5 | 1,328.873261 |
| 1 | 664.43663 |
| 2 | 332.218315 |
| 5 | 132.887326 |
| 10 | 66.443663 |
| 15 | 44.295775 |
| 20 | 33.221832 |
| 25 | 26.577465 |
| 50 | 13.288733 |
| 100 | 6.644366 |
| 250 | 2.657747 |
| 500 | 1.328873 |
| 1000 | 0.664437 |
Where these values come from
Every factor on this page is traced to the document that defines it. See the full provenance dataset or our methodology.
Miles/Gallon (UK) (mpg (UK))
Fuel Economy
Composite of a defined volume and a defined length. US and imperial gallons differ, so mpg figures are not interchangeable between them.
Source: NIST Special Publication 811, Guide for the Use of the International System of Units
National Institute of Standards and Technology (US) · Reviewed 2026-07-01
Gallon (US)/100mi (gal/100mi)
Fuel Economy
Composite of a defined volume and a defined length. US and imperial gallons differ, so mpg figures are not interchangeable between them.
Source: NIST Special Publication 811, Guide for the Use of the International System of Units
National Institute of Standards and Technology (US) · Reviewed 2026-07-01
How to Convert Miles/Gallon (UK) to Gallon (US)/100mi
This conversion uses an offset formula, so it cannot be described by a single multiplication factor.
Formula: gal/100mi = mpg (UK) × 664.4366303531
Reverse: mpg (UK) = gal/100mi × 664.4366303531
Step-by-Step Example
- Start with your value in Miles/Gallon (UK). For example: 5 mpg (UK)
- Apply gal/100mi = mpg (UK) × 664.4366303531
- The result is: 132.887326 gal/100mi
Miles/Gallon (UK) and Gallon (US)/100mi Relationship
This calculation facilitates standardized conversion between recognized units of fuel economy. Unlike simple multiplicative factors, this conversion follows an affine calculation model: gal/100mi = mpg (UK) × 664.4366303531. Understanding the relationship between Miles/Gallon (UK) and Gallon (US)/100mi is essential for accurate calculations in physics, engineering, commerce, and daily applications.
About Miles/Gallon (UK)
The Miles/Gallon (UK) (symbol: mpg (UK)) is a recognized unit in the Standard measurement framework, utilized within fuel economy applications for precision and standardized data representation.
Common uses of Miles/Gallon (UK): fuel economy calculations, engineering and science, education.
About Gallon (US)/100mi
The Gallon (US)/100mi (symbol: gal/100mi) is a recognized unit in the US Customary / Imperial measurement framework, utilized within fuel economy applications for precision and standardized data representation.
Common uses of Gallon (US)/100mi: fuel economy calculations, engineering and science, education.
Frequently Asked Questions
- What is 21 Miles/Gallon (UK) in Gallon (US)/100mi?
- 21 Miles/Gallon (UK) equals 31.63984 Gallon (US)/100mi.
- How many Gallon (US)/100mis are in 1 Miles/Gallon (UK)?
- There are exactly 664.4366303531 Gallon (US)/100mis in 1 Miles/Gallon (UK).
- What is the formula to convert Miles/Gallon (UK) to Gallon (US)/100mi?
- The formula to convert Miles/Gallon (UK) to Gallon (US)/100mi is: gal/100mi = mpg (UK) × 664.4366303531. For example, to convert 10 Miles/Gallon (UK)s to Gallon (US)/100mis, you would apply the formula to 10.
- What is a Miles/Gallon (UK)?
- The Miles/Gallon (UK) (symbol: mpg (UK)) is a recognized unit in the Standard measurement framework, utilized within fuel economy applications for precision and standardized data representation.
- What is a Gallon (US)/100mi?
- The Gallon (US)/100mi (symbol: gal/100mi) is a recognized unit in the US Customary / Imperial measurement framework, utilized within fuel economy applications for precision and standardized data representation.
- What are the common uses of Miles/Gallon (UK)?
- The Miles/Gallon (UK) is commonly used in fuel economy calculations, engineering and science, education.
Related Fuel Economy Conversions
Cite this page
UnitConvertLab. (2026). 21 Miles/Gallon (UK) to Gallon (US)/100mi. UnitConvertLab. Retrieved from https://unitconvertlab.com/convert/21-mpg_uk-to-gallon_per_100mi_us