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    Fuel Economy Conversion

    21 Miles/Gallon (US) to Kilometer/Liter

    Quick answer

    21 Miles/Gallon (US) (mpg) equals

    8.928018 km/L

    To convert 21 Miles/Gallon (US)s to Kilometer/Liters, multiply by 0.425143707. Therefore, 21 Miles/Gallon (US) (mpg) equals 8.928018 Kilometer/Liter (km/L).

    Formula: km/L = mpg × 0.425143707. Calculation: 21 × 0.425143707 = 8.928018 km/L.

    Convert Miles/Gallon (US) (mpg) to Kilometer/Liter (km/L) online with our free unit converter. In fuel economy, 1 mpg = 0.425144 km/L. Explore step-by-step conversion steps, mathematical formulas, and quick conversion reference tables below.

    Worked example: converting Miles/Gallon (US) to Kilometer/Liter

    1. Step 1 — start with the formula. km/L = mpg × 0.425143707
    2. Step 2 — substitute your figure. 21 mpg × 0.425143707
    3. Step 3 — read the result. 21 mpg = 8.928018 km/L
    4. Step 4 — check it in reverse. mpg = km/L × 2.3521458357 returns 21 mpg, which matches the figure you started with.

    Fuel Economy Converter

    11 units available

    Decimals:
    8.928018

    21 mpg = 8.928018 km/L

    Formula:

    km/L = mpg × 0.425143707

    With your value: 21 mpg = 8.92801785 km/L

    Other Miles/Gallon (US) to Kilometer/Liter conversions

    15 mpg to km/L16 mpg to km/L18 mpg to km/L20 mpg to km/L24 mpg to km/L25 mpg to km/L26 mpg to km/LFull Miles/Gallon (US) to Kilometer/Liter converter

    Miles/Gallon (US) to Kilometer/Liter Conversion Table

    Miles/Gallon (US) (mpg)Kilometer/Liter (km/L)
    0.50.212572
    10.425144
    20.850287
    52.125719
    104.251437
    156.377156
    208.502874
    2510.628593
    5021.257185
    10042.514371
    250106.285927
    500212.571854
    1000425.143707

    Kilometer/Liter to Miles/Gallon (US) Conversion Table

    Kilometer/Liter (km/L)Miles/Gallon (US) (mpg)
    0.51.176073
    12.352146
    24.704292
    511.760729
    1023.521458
    1535.282188
    2047.042917
    2558.803646
    50117.607292
    100235.214584
    250588.036459
    5001,176.072918
    10002,352.145836

    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 (US) (mpg)

    Fuel Economy

    Exact conversion

    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

    Kilometer/Liter (km/L)

    Fuel Economy

    Exact conversion

    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 (US) to Kilometer/Liter

    To convert from Miles/Gallon (US) (mpg) to Kilometer/Liter (km/L), multiply the value by 0.425143707.

    Formula: km/L = mpg × 0.425143707

    Reverse: mpg = km/L × 2.3521458357

    Step-by-Step Example

    1. Start with your value in Miles/Gallon (US). For example: 5 mpg
    2. Multiply by the conversion factor: 5 x 0.425143707
    3. The result is: 2.125719 km/L

    Miles/Gallon (US) and Kilometer/Liter Relationship

    This calculation facilitates standardized conversion between recognized units of fuel economy. Since 1 Miles/Gallon (US) represents a fraction of a Kilometer/Liter (1 Kilometer/Liter ≈ 2.3521 Miles/Gallon (US)s), the Kilometer/Liter is the larger measurement interval. Understanding the relationship between Miles/Gallon (US) and Kilometer/Liter is essential for accurate calculations in physics, engineering, commerce, and daily applications.

    About Miles/Gallon (US)

    Miles per gallon (mpg) is the standard measure of fuel economy in the United States.

    Common uses of Miles/Gallon (US): car window stickers, fuel costs, environmental metrics.

    About Kilometer/Liter

    Kilometers per liter (km/L) measures how many kilometers a vehicle can travel on one liter of fuel.

    Common uses of Kilometer/Liter: fuel efficiency, vehicle specs, travel planning.

    Frequently Asked Questions

    What is 21 Miles/Gallon (US) in Kilometer/Liter?
    21 Miles/Gallon (US) equals 8.928018 Kilometer/Liter.
    How many Kilometer/Liters are in 1 Miles/Gallon (US)?
    There are exactly 0.425143707 Kilometer/Liters in 1 Miles/Gallon (US). This means the conversion factor from Miles/Gallon (US) to Kilometer/Liter is 0.425143707.
    What is the formula to convert Miles/Gallon (US) to Kilometer/Liter?
    The formula to convert Miles/Gallon (US) to Kilometer/Liter is: km/L = mpg × 0.425143707. For example, to convert 10 Miles/Gallon (US)s to Kilometer/Liters, you would multiply 10 by 0.425143707.
    What is a Miles/Gallon (US)?
    Miles per gallon (mpg) is the standard measure of fuel economy in the United States.
    What is a Kilometer/Liter?
    Kilometers per liter (km/L) measures how many kilometers a vehicle can travel on one liter of fuel.
    What are the common uses of Miles/Gallon (US)?
    The Miles/Gallon (US) is commonly used in car window stickers, fuel costs, environmental metrics.

    Related Fuel Economy Conversions

    Liter/100km → Kilometer/LiterMiles/Gallon (US) → Liter/100kmMiles/Gallon (US) → Miles/Gallon (UK)Miles/Gallon (US) → Mile/LiterMiles/Gallon (US) → Gallon (US)/100miMiles/Gallon (US) → Gallon (UK)/100miMiles/Gallon (US) → Kilometer/Gallon (US)Miles/Gallon (US) → Kilometer/Gallon (UK)Miles/Gallon (US) → Meter/Liter

    Cite this page

    UnitConvertLab. (2026). 21 Miles/Gallon (US) to Kilometer/Liter. UnitConvertLab. Retrieved from https://unitconvertlab.com/convert/21-mpg_us-to-km_per_liter