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Fuel Economy Calculator

Calculate your car's fuel consumption — enter distance driven and fuel used, get L/100km or MPG with cost per kilometer/mile

km
liters
$ per liter

Fuel Consumption

8.00 L/100km

29.40 MPG (US) / 35.31 MPG (UK)

Excellent Average High

Good fuel economy

Calculation

(8 L ÷ 100 km) × 100 = 8.00 L/100km

About This Tool

Knowing your car's real fuel consumption helps you budget for trips, compare vehicles, and spot problems early. A sudden jump in fuel use can signal maintenance issues — underinflated tires, dirty air filters, or engine problems. This calculator works both ways: metric (liters per 100 km) and imperial (miles per gallon). Fill up your tank, reset the trip odometer, drive until you need gas again, fill up and note the liters/gallons. Enter the numbers here and get your exact fuel economy instantly. The optional cost field shows you what each kilometer or mile actually costs to drive — useful for comparing commute routes, planning road trips, or deciding whether that fuel-efficient car is worth the premium.

How to Use

1. Fill your tank completely at a gas station 2. Reset your trip odometer to zero 3. Drive normally until you need to refuel 4. Fill up again and note how much fuel you put in 5. Note the distance on your trip odometer 6. Enter both numbers into this calculator 7. Toggle between metric (L/100km) and imperial (MPG) as needed 8. Optionally enter fuel price to see your cost per distance

Formula

Metric (L/100km): Fuel consumption = (Liters used ÷ Kilometers driven) × 100 Imperial (MPG): Fuel economy = Miles driven ÷ Gallons used Conversion: MPG (US) = 235.215 ÷ L/100km MPG (UK) = 282.481 ÷ L/100km Cost per distance: Cost per km = (L/100km ÷ 100) × Price per liter Cost per mile = Price per gallon ÷ MPG

Frequently Asked Questions

What is a good fuel consumption in L/100km?
For modern cars: 5-6 L/100km is excellent (small efficient cars, hybrids), 7-9 L/100km is good (most sedans and small SUVs), 10-12 L/100km is average (larger SUVs, older cars), and 13+ L/100km is high (trucks, sports cars, or maintenance issues). Electric vehicles measure in kWh/100km instead.
What is good MPG for a car?
In the US: 30-40 MPG is excellent (hybrids, efficient compacts), 25-30 MPG is good (most sedans), 20-25 MPG is average (SUVs, crossovers), and under 20 MPG is low (trucks, performance cars). EPA ratings are often optimistic — real-world MPG is typically 10-20% lower.
How do I convert L/100km to MPG?
Divide 235.215 by your L/100km to get US MPG, or divide 282.481 to get UK (Imperial) MPG. For example: 8 L/100km = 235.215 ÷ 8 = 29.4 MPG (US) or 35.3 MPG (UK). The difference is because a UK gallon is larger (4.546 L vs 3.785 L).
Why is my fuel consumption higher than the manufacturer's rating?
Manufacturer ratings are measured in ideal lab conditions. Real-world factors that increase consumption: city driving with frequent stops, aggressive acceleration, speeding (fuel use rises sharply above 100 km/h / 60 mph), cold weather, AC use, roof racks, underinflated tires, extra weight, and poor maintenance. A 20-30% difference from lab ratings is normal.
How do I calculate fuel cost for a trip?
Multiply the trip distance by your fuel consumption rate, then multiply by fuel price. Example: 500 km trip at 8 L/100km with fuel at $1.50/L = (500 × 8 ÷ 100) × 1.50 = 40 L × $1.50 = $60. This calculator does this math for you — just enter the price per liter or gallon.
What's the difference between US and UK gallons?
A US gallon is 3.785 liters, while a UK (Imperial) gallon is 4.546 liters — about 20% larger. This means UK MPG numbers are always higher than US MPG for the same car. When comparing fuel economy across countries, always check which gallon is being used, or compare in L/100km which is universal.
Does AC use more fuel?
Yes, air conditioning typically increases fuel consumption by 5-15%, depending on the car and conditions. At highway speeds, AC is more efficient than opening windows (which creates drag). In city traffic or at low speeds, opening windows is more efficient. Modern AC systems are more efficient than older ones.

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