Fuel Efficiency Calculator
Calculate real-world fuel economy from distance driven and fuel used. Choose EU for L/100km, US for mpg (US), or UK for mpg (UK), then enter the numbers from a tank fill, receipt, or trip log.
Examples
EU tank fill
500 km driven on 34 L of fuel — 6.8 L/100km.
- Driving system
- EU
- Distance driven
- 500 km
- Fuel used
- 34 L
Result
6.8 L/100km
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How It Works
Formula
Variables, symbols and units
- Distance driven(km or mi)
- Fuel consumed over that distance(L or gal)
- Miles per gallon for the selected US or UK gallon system
- Litres consumed per 100 kilometres(L/100km)
Calculation method explained
Choose the driving system. In EU mode, fuel economy is litres used divided by kilometres driven, multiplied by 100. In US and UK modes, fuel economy is miles driven divided by gallons used.
Examples
EU tank fillEU · 500 km → 6.8 L/100km
500 km driven on 34 L of fuel — 6.8 L/100km.
- Driving system
- EU
- Distance driven
- 500 km
- Fuel used
- 34 L
- Result
- 6.8 L/100km
US gas mileageUS · 300 mi → 30 mpg (US)
300 miles driven on 10 gallons — 30 mpg (US).
- Driving system
- US
- Distance driven
- 300 mi
- Fuel used
- 10 US gal
- Result
- 30 mpg (US)
UK tank checkUK · 360 mi → 45 mpg (UK)
360 miles driven on 8 UK gallons — 45 mpg (UK).
- Driving system
- UK
- Distance driven
- 360 mi
- Fuel used
- 8 UK gal
- Result
- 45 mpg (UK)
Frequently Asked Questions
How is fuel efficiency calculated?
For EU mode, the calculator uses fuel used divided by distance, then multiplied by 100 to get L/100km. For US and UK modes, it divides miles driven by gallons used to get mpg.
What is a good fuel efficiency rating?
There is no universal cutoff. Lower L/100km or higher mpg means less fuel used for the same distance. This calculator also groups results into broad built-in bands for the selected unit system.
Does driving speed affect fuel efficiency?
This calculator only uses the distance and fuel values you enter. To compare trips, enter measurements that were recorded in the same way.
Where did the trip fuel cost mode go?
Trip fuel cost is now a separate Driving Cost Calculator so this page can focus on measured fuel economy from distance and fuel used.
What is the difference between US and UK gallons?
US mpg and UK mpg use different gallon units. Use the driving system switch to choose the unit that matches your fuel measurement.