Fuel Economy Converter

Convert between MPG (US & UK), km/L, and L/100km instantly. Supports both efficiency (higher = better) and consumption (lower = better) units.

Value

From

Common Fuel Economy Conversions

MPG (US)	MPG (UK)	km/L	L/100km
20	24.02	8.50	11.76
25	30.03	10.63	9.41
30	36.03	12.75	7.84
35	42.04	14.88	6.72
40	48.04	17.01	5.88
50	60.05	21.26	4.71

Frequently Asked Questions

US MPG uses the US gallon (3.785 L), while UK MPG uses the Imperial gallon (4.546 L). Since the Imperial gallon is about 20% larger, the same car gets ~20% more UK MPG than US MPG. A car rated at 30 US MPG is approximately 36 UK MPG. Always check which gallon a fuel economy rating uses.

L/100km is a consumption metric (lower = more efficient), while MPG and km/L are efficiency metrics (higher = more efficient). They have an inverse relationship: L/100km = 100 ÷ km/L. A car using 5 L/100km is more efficient than one using 8 L/100km.

To convert US MPG to L/100km: divide 235.215 by the MPG value. For UK MPG divide 282.481 by the value. For example, 30 US MPG = 235.215/30 ≈ 7.84 L/100km. To go the other way, divide those constants by the L/100km value to get MPG.

L/100km: EU countries, Canada, Australia, South Africa. km/L: Japan, India, Korea, parts of Asia. US MPG: United States. UK MPG: United Kingdom (though L/100km is also displayed). The EU mandates CO₂ g/km alongside fuel economy figures on new cars.

MPG measures distance per unit of fuel (higher = better), while L/100km measures fuel per unit of distance (lower = better). They have an inverse relationship: L/100km = 235.215 ÷ US MPG. This means improving from 20 to 25 MPG saves more fuel than going from 40 to 50 MPG, even though both are 5 MPG gains.

Key techniques to improve fuel economy: maintain proper tire pressure (saves 0.5–3%), reduce highway speed (fuel use rises with speed squared — driving 70 mph vs 60 mph uses ~17% more fuel), avoid rapid acceleration, remove roof racks when not in use, and keep the engine properly maintained. Air conditioning increases fuel use by up to 10–15%.

EPA fuel economy figures are measured on a chassis dynamometer in controlled lab conditions and are adjusted to reflect real-world driving. Still, real-world mpg typically runs 10–20% below the EPA estimate due to aggressive driving, cold weather, hills, load, and air conditioning. The EPA provides city, highway, and combined ratings; combined is typically closest to average driving.

MPGe (miles per gallon equivalent) compares electric vehicle efficiency to gasoline. The EPA defines 1 gallon of gasoline ≈ 33.7 kWh of energy, so MPGe = miles driven per 33.7 kWh used. A Tesla Model 3 rates about 132 MPGe combined. Higher MPGe means lower energy cost per mile driven.

Hybrids typically achieve 40–60 MPG (4–6 L/100km) in combined driving, compared to 25–35 MPG for comparable conventional cars. Full battery electric vehicles (BEVs) achieve the equivalent of 100–140 MPGe. PHEVs (plug-in hybrids) can run on electricity for short trips then switch to gasoline. EVs have no tailpipe emissions but their total environmental impact depends on how electricity is generated.

For MPG: Cost per mile = fuel price per gallon ÷ MPG. For example, $3.50/gal ÷ 30 MPG = $0.117/mile. For L/100km: Cost per km = (fuel price per liter × L/100km) ÷ 100. For example, $1.50/L × 7 L/100km ÷ 100 = $0.105/km. Multiply by distance to get trip fuel cost.

About This Fuel Economy Converter

This free fuel economy converter converts between miles per gallon (US mpg and UK mpg), litres per 100 km (L/100 km), and kilometres per litre (km/L). Enter a value in any unit for instant conversion.

When to use this converter

Comparing vehicle efficiency ratings between countries
Converting MPG to L/100 km for European driving or car shopping
Evaluating fuel cost over a planned road trip

Standards & References

How It Works

Enter Economy

Enter any fuel economy value. The converter handles the inverse relationship of L/100km automatically.

Pick Units

Choose from US MPG, UK MPG, km/L, and L/100km — covering all major fuel economy standards worldwide.

Instant Result

Results are shown immediately. The reference table lists typical efficiency values across all four units for easy comparison.

Common Use Cases

Car Shopping

Compare fuel economy of cars from different countries by converting between MPG (US/UK), km/L, and L/100km.

International Travel

Understand rental car fuel economy ratings when driving abroad — convert between local fuel economy units and what you're used to at home.

Fuel Cost Planning

Convert fuel economy to estimate trip fuel costs and compare fuel efficiency of different vehicles before a long journey.

Eco Comparisons

Compare environmental footprints of different vehicles across international standards to make greener choices.

Fleet Management

Convert and standardize fuel economy data from international fleets into a single unit for reporting and benchmark comparisons.

Automotive Journalism

Convert fuel economy figures cited in international press reviews to local units for your readership or publication's preferred format.

Related Converters

View all articles

The MPG Illusion: Why 10→20 MPG Saves More Fuel Than 30→50 MPG

Going from 10 MPG to 20 MPG saves nearly 4x more fuel than going from 30 MPG to 50 MPG — even though the second jump looks "bigger" in MPG points. Here's why MPG's "distance per fuel" framing is the inverse of what actually determines fuel costs, why L/100km-style metrics avoid this "MPG illusion" entirely, and why fuel-economy improvements at the low end of the scale represent disproportionately larger real savings.

Jun 14, 2026

Hypermiling Techniques: The Driving Habits That Measurably Improve Fuel Economy

Driving at 70 mph instead of 80 mph cuts fuel consumption by approximately 25% on the motorway. Here's the aerodynamics behind that, plus tyre pressure, anticipatory braking, route planning, and the other hypermiling techniques with measurable impact.

Jun 13, 2026

EV Efficiency vs Petrol: What kWh/100km Actually Means for Your Running Costs

EVs measure efficiency in kWh/100km or miles per kWh — and once you convert those numbers to petrol equivalents, the running cost comparison becomes clear. Here's the full calculation with home charging vs. public charging, and why winter dramatically affects real-world range.

Jun 9, 2026