Gas Mileage & Fuel Economy Calculator
Track gas mileage and convert fuel efficiency across US, UK, and metric standards.
Fuel Economy & MPG Calculator
Convert a measured drive and fuel used to US MPG, Imperial MPG, and L/100 km.
Equivalent fuel economy
US miles per gallon
30.00
- Imperial miles per gallon
- 36.03
- Liters per 100 km
- 7.84
Uses the measured fuel volume you provide. US and Imperial gallons differ; vehicle displays, test methods, and real-world driving conditions may differ.
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What This Calculator Does
The Gas Mileage & Fuel Economy Calculator computes vehicle fuel efficiency from distance traveled and fuel consumed. It displays equivalent ratings across US miles per gallon (MPG), UK Imperial miles per gallon, and metric liters per 100 kilometers (L/100 km).
How It Works
Distance and fuel volume are converted to standard units. US MPG is miles divided by US gallons. Imperial MPG is miles divided by UK imperial gallons (1 Imperial gallon ≈ 1.20095 US gallons). L/100 km is calculated as (liters / kilometers) × 100.
Example
Driving 300 miles on 10 US gallons of gasoline yields 30.00 US MPG, 36.03 Imperial MPG, and 7.84 L/100 km.
Formula
US MPG = Miles / US GallonsImperial MPG = Miles / Imperial Gallons = US MPG × 1.20095L/100 km = 235.215 / US MPG = (Liters / Kilometers) × 100Reading the Results
US miles per gallon
Standard American fuel efficiency rating indicating distance covered per US liquid gallon.
Imperial miles per gallon
United Kingdom and Commonwealth fuel rating based on the larger Imperial gallon (4.546 liters).
Liters per 100 km
Standard metric fuel consumption figure indicating fuel volume needed to travel 100 kilometers.
Frequently Asked Questions
Why is UK MPG higher than US MPG?
A UK Imperial gallon is about 20% larger than a US liquid gallon (4.546 liters vs 3.785 liters), so a car travels more miles per Imperial gallon.
How do I accurately measure my car MPG?
Fill your tank completely and reset the trip odometer. Drive normally until your next fill-up, fill to full again, and divide the trip miles by the exact gallons pumped.
Why is a lower L/100 km number better?
L/100 km measures consumption (fuel used per distance), whereas MPG measures efficiency (distance per fuel). Lower consumption means better fuel economy.