Fuel Economy Converter
The Fuel Economy Converter converts between U.S. miles per gallon (MPG), liters per 100 kilometers (L/100 km), and kilometers per liter (km/L). Because L/100 km is an inverse measure, the converter handles the non-linear relationship correctly rather than applying a simple multiplier. Because MPG and km/L measure distance per unit of fuel while L/100 km measures fuel per unit of distance, equal MPG improvements don't save equal amounts of fuel — going from 15 to 20 MPG cuts fuel use per 100 miles from about 6.67 to 5 gallons (a 1.67-gallon savings), while going from 40 to 45 MPG saves only about 0.28 gallons over the same distance. This "MPG illusion" is why L/100 km, which scales linearly with actual fuel consumed, is generally considered the more intuitive unit for comparing efficiency gains.
How This Tool Works
Enter a fuel economy figure, choose the unit you have and the unit you want, and read the converted result.
Formula & Method
Conversions pass through kilometers per liter as a common base. 1 US MPG ≈ 0.425144 km/L, and L/100 km = 100 ÷ km/L (an inverse relationship, so higher MPG means lower L/100 km).
Example Calculation
30 US MPG converts to km/L by multiplying by the mile-to-km factor and dividing by the gallon-to-liter factor: (30 × 1.609344) ÷ 3.78541 = 48.28032 ÷ 3.78541 ≈ 12.75 km/L. From km/L, L/100 km is found by inverting: 100 ÷ 12.75 ≈ 7.84 L/100 km. Going the other direction, a European spec sheet listing 6.0 L/100 km first converts to km/L as 100 ÷ 6.0 ≈ 16.67 km/L, then to US MPG as (16.67 × 3.78541) ÷ 1.609344 ≈ 39.2 MPG.
Frequently Asked Questions
Does this use US or imperial MPG?+
This converter uses U.S. MPG (U.S. miles per U.S. gallon). A UK imperial gallon is larger, so imperial MPG figures are about 20% higher than U.S. MPG for the same car.
Why isn't L/100 km a simple multiple of MPG?+
L/100 km measures fuel used per distance, while MPG and km/L measure distance per fuel — they are inversely related, so the conversion divides rather than multiplies. That is why lower L/100 km and higher MPG both mean better efficiency.
How do I convert MPG to km/L?+
Multiply U.S. MPG by about 0.425144. For example, 30 MPG × 0.425144 ≈ 12.75 km/L.
Why does going from 15 to 20 MPG save more fuel than going from 40 to 45 MPG?+
Because MPG measures distance per gallon, not fuel used — at 15 MPG a 100-mile trip burns 6.67 gallons, and at 20 MPG it burns 5 gallons, a savings of 1.67 gallons. At 40 MPG the same trip burns 2.5 gallons, and at 45 MPG it burns 2.22 gallons, a savings of only 0.28 gallons — six times less fuel saved for the same 5-MPG improvement. This is why L/100 km, which scales linearly with actual fuel burned, is often considered the more honest efficiency metric.
How do I convert a US MPG window sticker to L/100 km for a car I'm importing from Europe?+
Convert through km/L: multiply MPG by 1.609344 and divide by 3.78541 to get km/L, then divide 100 by that km/L figure. For example, a 35 MPG car converts to about 14.88 km/L, which works out to roughly 6.72 L/100 km.
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<a href="https://everyfix.net/tools/fuel-economy-converter/">Fuel Economy Converter</a> by <a href="https://everyfix.net">EveryFix</a>Related Tools
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