Calculators · Fuel

Fuel economy converter and trip cost calculator

Fuel economy is quoted in different ways around the world: litres per 100 km in Europe, miles per gallon in the United States and the United Kingdom (with different gallons), and kilometres per litre in much of Asia. These calculators convert between all of them, work out the fuel and cost of a trip, and show what an improvement in economy is worth over a year.

Fuel economy unit converter

Converts any economy figure into all common units at once. Note that l/100 km measures fuel used, so lower is better, while MPG and km/L measure distance, so higher is better.

Results
Litres per 100 km—l/100 kmFuel used over 100 km — lower is better.
Miles per US gallon—MPG USUsed on US window stickers and by FuelEconomy.gov.
Miles per UK gallon—MPG UKUsed in the United Kingdom — about 20% higher than US MPG for the same car.
Kilometres per litre—km/LUsed in Japan, India and much of Latin America.

Formula
MPG(US) = 235.215 / (l/100 km)
MPG(UK) = 282.481 / (l/100 km)
km/L = 100 / (l/100 km)

Trip fuel and cost

Estimates how much fuel a journey will use and what it will cost, from the distance, the car’s consumption and the price of fuel. Use a price in any currency; the result comes out in the same currency.

Results
Fuel used—Total fuel for the trip.
Fuel cost—currencyFuel used × price per litre.

Formula
fuel = distance × consumption / 100
cost = fuel × price

Annual savings from better economy

Shows how much fuel and money a more economical car saves over a year. It helps put a price on the difference between two cars you are choosing between.

Results
Fuel saved per year—Difference in fuel used over the year.
Money saved per year—currencyFuel saved × price per litre.

Formula
saved = distance × (old − new) / 100
money = saved × price

Worked example: a 500 km trip

  1. A car rated at 31.8 MPG (US) uses 235.215 / 31.8 = 7.4 l/100 km.
  2. Over 500 km it uses 500 × 7.4 / 100 = 37 litres.
  3. At 1.20 per litre the fuel costs 37 × 1.20 = 44.40.
  4. Switching to a car using 6.0 instead of 8.0 l/100 km saves 300 litres over 15,000 km a year.

Fuel economy equivalents

l/100 kmMPG (US)MPG (UK)km/L
4.058.870.625.0
5.047.056.520.0
6.039.247.116.7
8.029.435.312.5
10.023.528.210.0
12.019.623.58.3
15.015.718.86.7

Related

Power-to-weight and torque-to-weight calculatorGear ratio, road speed and wheel torque calculatorFuel cost calculator for any carRunning costs by classCar rankings

About these results

Results are theoretical estimates from standard engineering formulas. Real-world figures depend on conditions these formulas do not capture. Always follow the manufacturer's specifications for maintenance, loading and safety decisions.

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