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Fuel Efficiency Converter

MPG ↔ L/100km ↔ km/L — with EU rating, annual cost & vehicle comparison

From
To
Annual Cost Estimator
Result
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Enter a value to convert
2 MPG150 MPG
MPG (US)
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L/100km
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MPG (Imp)
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km/L
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Annual Cost
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CO₂ Emissions
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You beat
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of vehicles

Enter a value in the Converter tab to compare

Click any row to load that vehicle into the converter

Vehicle MPG / MPGe L/100km km/L Tier
Fleet Comparison Chart — your value shown as dashed line
Chart: vehicle chart.
Conversion Formulas
MPG US → L/100km 235.214 ÷ MPG Inverse relationship
L/100km → MPG US 235.214 ÷ L/100km Same constant, inverse
MPG Imp → L/100km 282.481 ÷ MPG Imp Imperial gallon = 4.546 L
km/L → L/100km 100 ÷ km/L Reciprocal scale
MPG US → MPG Imp MPG US × 1.20095 UK gallon ~20% larger
CO₂ Emissions (L/100km × 2310) ÷ 100 g/km (gasoline)
Conversion Matrix — click any cell to load that conversion

Note: MPG ↔ L/100km is an inverse (non-linear) relationship. The matrix shows actual converted values, not simple multipliers.

Key Constants
US Gallon3.785 411 784 L
Imperial Gallon4.546 09 L
1 Mile1.609 344 km
MPG US→Imp Factor× 1.200 95
Gasoline CO₂2 310 g/L
Diesel CO₂2 640 g/L
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How to Use This Calculator

1

Select Your Unit System

Choose MPG (US or Imperial), L/100km, or km/L as your starting unit in the Converter tab.

2

Enter the Efficiency Value

Type your fuel-efficiency figure. The EU tier, spectrum bar, and all stats update instantly.

3

Compare & Export

Switch to the Vehicles tab to see how you rank, or Formulas for the conversion matrix. Export to CSV anytime.

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Formula & Methodology

MPG to L/100km
L/100km = 235.214 ÷ MPG
The inverse relationship means higher MPG corresponds to lower L/100km.
km/L to MPG (US)
MPG = km/L × 2.35215
Multiply kilometers per liter by 2.352 to get US miles per gallon.
MPG (US) to MPG (UK)
MPG(UK) = MPG(US) × 1.20095
A UK gallon is about 20% larger than a US gallon, so UK MPG figures are always higher for the same vehicle.

About this calculation · Accuracy & Methodology

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Key Terms

MPG (US) Miles per US gallon; the standard fuel-economy measure in the United States.
MPG (Imperial) Miles per Imperial gallon; used in the UK. One Imperial gallon equals 4.546 liters.
L/100km Liters consumed per 100 kilometers; the metric fuel-consumption standard used in Europe and much of the world.
km/L Kilometers traveled per liter of fuel; common in Japan and parts of Asia.
MPGe Miles per gallon equivalent; for electric vehicles. The EPA equates 33.7 kWh to one gallon of gasoline.
EU Efficiency Tier A-to-F label adapted from EU appliance energy ratings. A+ indicates exceptional efficiency (≥55 MPG US); F indicates very low efficiency (<12 MPG US).
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Real-World Examples

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European family car — 6.0 L/100km

Input: 6.0 L/100km → MPG US

Result
= 39.2 MPG US

= 39.2 MPG US — efficient by US standards, Tier B on the EU label

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Understanding Fuel Efficiency Metrics

MPG vs. L/100km: A Non-Linear Relationship

Because MPG and L/100km are inversely related, improving from 15 to 20 MPG saves far more fuel per mile than improving from 35 to 40 MPG. This is why many policy experts prefer L/100km — it scales linearly with actual consumption and makes fuel savings easy to compare across vehicles.

The EU Efficiency Label Explained

The A+ to F rating shown by this converter is adapted from EU appliance energy labelling standards and applied to vehicles by MPG US threshold. A+ (≥55 MPG) covers the best hybrids and EVs. C tier (25–34 MPG) represents the average new car sold in the US. F tier (<12 MPG) includes heavy trucks and exotic performance cars.

Real-World vs. Rated Efficiency

EPA laboratory test-cycle figures often differ from on-road performance by 10–25%. Aggressive driving, cold weather, roof racks, and low tire pressure all reduce real-world efficiency. When comparing vehicles, use the same test standard (EPA, WLTP, or NEDC) and consider your personal driving profile.

Electric Vehicles and MPGe

MPGe (miles per gallon equivalent) allows EVs to be compared on the same scale as combustion vehicles. The EPA defines 33.7 kWh as the energy equivalent of one gallon of gasoline. A Tesla Model 3 Long Range rated at 141 MPGe consumes about 24 kWh per 100 miles — dramatically less than any gasoline vehicle.

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Frequently Asked Questions

Advanced Why do US and UK MPG ratings differ for the same car?
The US gallon (3.785 L) and Imperial gallon (4.546 L) differ by about 20%. A car rated at 45 MPG Imperial equals roughly 37.5 MPG US. Always check which standard is being used when comparing international specs.
General Is L/100km a better unit than MPG?
L/100km scales linearly with fuel consumption, making it easier to calculate actual fuel costs and compare savings. MPG is intuitive in the US but non-linear — a 5 MPG improvement from 15 to 20 MPG saves twice as much fuel as 5 MPG from 30 to 35 MPG.
General What does MPGe mean for electric vehicles?
MPGe (miles per gallon equivalent) converts electricity consumption into a gasoline-equivalent metric. The EPA defines 33.7 kWh = 1 gallon of gasoline energy. A Tesla Model 3 at 141 MPGe uses roughly 24 kWh per 100 miles.
Basics How is annual fuel cost calculated?
Annual Cost = (Annual Miles ÷ MPG) × Gas Price per Gallon. For example, driving 12,000 miles at 30 MPG with gas at $3.50/gallon costs $1,400/year. Adjust the Gas Price and Miles/Year fields to match your situation.
General How much CO₂ does a gasoline car emit per km?
Burning one liter of gasoline produces approximately 2,310 g of CO₂. This converter uses that constant to compute g/km: CO₂ (g/km) = (L/100km × 2,310) ÷ 100. A 30 MPG car emits about 192 g/km.
Basics What is a good fuel efficiency rating?
The US average is around 28 MPG. Anything above 35 MPG is considered efficient for a gasoline car. Hybrids typically achieve 45–60 MPG. The EU Energy Label used in this converter classifies ≥45 MPG as "A" tier and ≥55 MPG as "A+".

Real-World Reference

🚗US Avg Car28 MPG = 8.4 L/100km
🔋Toyota Prius57 MPG = 4.1 L/100km
🚛Semi Truck6 MPG = 39 L/100km
✈️Boeing 747~0.2 MPG = 1,200 L/100km
🏍️Motorcycle45 MPG = 5.2 L/100km
⚡Tesla Model 3141 MPGe = 1.67 L eq./100km

Quick Conversion Table

MPG (US)L/100kmkm/LContext
1023.54.3Large truck / Heavy SUV
1515.76.4Full-size pickup
2011.88.5Older mid-size sedan
259.410.6Average crossover
307.812.8Modern sedan
405.917.0Efficient compact
504.721.3Hybrid
802.934.0Near-EV equivalent