Fuel Economy Converter — MPG, km/L, L/100km Explained

Fuel economy is one of those specs that car buyers care about deeply but find confusing because different countries measure it differently — and not even in compatible ways. The US uses miles per gallon (mpg). Europe uses liters per 100 kilometers (L/100km). Some Asian markets use kilometers per liter (km/L). The annoying thing is that mpg and km/L work in the same direction (higher is better), but L/100km works backwards (lower is better).

The CalcHub fuel economy converter handles all three plus imperial mpg.

Fuel Economy Conversion Table

From	To	Formula
1 US mpg	L/100km	235.215 ÷ mpg
1 US mpg	km/L	mpg × 0.425144
1 L/100km	US mpg	235.215 ÷ L/100km
1 km/L	US mpg	km/L × 2.35215
1 UK mpg (imperial)	L/100km	282.481 ÷ mpg
1 UK mpg	US mpg	UK mpg × 0.832674

Quick Reference: Common Fuel Economy Values

US mpg	km/L	L/100km	What Kind of Car
15 mpg	6.4 km/L	15.7 L/100km	Truck or large SUV
25 mpg	10.6 km/L	9.4 L/100km	Average midsize sedan
35 mpg	14.9 km/L	6.7 L/100km	Efficient compact
50 mpg	21.3 km/L	4.7 L/100km	Hybrid (Toyota Prius class)
70 mpg	29.8 km/L	3.4 L/100km	Best plug-in hybrids
100+ mpg	—	<2.4 L/100km	Electric vehicles (MPGe)

The Key Difference That Catches Everyone

MPG and km/L are "efficiency" units — you want them higher. Doubling the number means you use half the fuel. L/100km is a "consumption" unit — you want it lower. Halving the number means you use half the fuel.

The implication is that improvements in L/100km aren't linear. Going from 20 L/100km to 10 L/100km saves you 10 liters per 100 km traveled. But going from 10 L/100km to 5 L/100km also saves 5 liters — the same absolute improvement requires a much larger percentage change. This is why fuel economy standards in the US (CAFE standards) measured in mpg systematically over-reward already-efficient vehicles.

How to Use the CalcHub Fuel Economy Converter

1. Visit calchub.in and open the Fuel Economy Converter
2. Enter the fuel economy figure from your car's spec sheet, sticker, or trip computer
3. Select the original unit
4. View the equivalent in all other fuel economy units

Useful for comparing car specs across countries — an EU car rated at 5.5 L/100km is the equivalent of about 42.8 US mpg.

US vs UK Gallons: The Extra Complication

A US gallon is 3.785 liters. A UK imperial gallon is 4.546 liters. That's why a UK mpg figure is always higher than the equivalent US mpg figure for the same car — the UK gallon holds more fuel.

A car that does 40 UK mpg actually achieves about 33.3 US mpg. Car comparison sites that mix these up will show misleadingly efficient numbers for British cars.

Calculating Your Real Fuel Cost

Once you know your fuel economy, estimating costs is straightforward:

• Cost per mile (US): Fuel price ($/gallon) ÷ mpg
• Cost per km (metric): Fuel price (per liter) × L/100km ÷ 100

Example: Gas costs $3.50/gallon and your car gets 28 mpg. That's $3.50 ÷ 28 = $0.125 per mile. A 300-mile road trip costs about $37.50 in fuel.

What does MPGe mean for electric vehicles?

MPGe (miles per gallon equivalent) is a US EPA rating for EVs and plug-in hybrids. It compares electricity consumption to gasoline energy content — 1 gallon of gasoline contains roughly 33.7 kWh of energy. So an EV that uses 33.7 kWh per 100 miles would get 100 MPGe. Higher MPGe means the EV uses electricity more efficiently.

Why does my fuel economy get worse in winter?

Cold temperatures reduce engine efficiency, increase air density, and cause tires to lose pressure. Cold engines burn more fuel warming up. Ethanol-blended winter gasoline has slightly less energy per gallon. Winter fuel economy can be 10–20% worse than summer economy for gasoline vehicles.

How accurate is the mpg shown on my trip computer?

Modern trip computers are typically within 1–3% of actual fuel economy. They calculate it from injector pulse times and fuel flow sensors. Manual calculations (fill up, drive to empty, fill up again, divide miles by gallons) are generally the most accurate cross-check.

Related Converters

• Volume Converter — liters, gallons
• Speed Converter — mph, km/h
• Length Converter — miles, kilometers