MPG Calculator
Calculate your vehicle’s miles per gallon (MPG) quickly and accurately from distance driven and gallons used. Distinguish between US MPG and UK Imperial MPG, and convert directly to km/L and L/100km.
Direct Miles Per Gallon (MPG) Calculator
Formula: MPG = Miles Driven ÷ Gallons Used
Equivalent to 30.02 UK Imperial MPG
Bidirectional Multi-Unit Converter
Enter any efficiency rating below to see its exact mathematical equivalent across other systems.
MPG, km/L & L/100km Instant Converter
Bidirectional real-time conversion between US MPG, UK MPG, km/L, and L/100km
Enter any value below. All other three standards update automatically with exact SI physical conversions.
Worked Example:
You filled your tank to the brim, drove 500 miles on a road trip, and then refueled with 20 US gallons:
At $3.50 per gallon, total fuel cost was $70.00, resulting in exactly $0.14 per mile.
Important: US MPG vs. UK Imperial MPG
A common point of error when researching car fuel efficiency online is confusing US MPG with UK MPG. Because the UK Imperial gallon is approximately 20.095% larger than a US liquid gallon (4.546 liters vs. 3.785 liters), the same car will achieve a higher numerical MPG rating in the UK:
3.78541 Liters (231 cubic inches). Standard in the United States.
4.54609 Liters (277.42 cubic inches). Standard in the United Kingdom.
- Using tank capacity instead of fuel pumped: Do not divide trip miles by your vehicle’s total tank capacity (e.g. 15 gallons). You must only divide by the exact amount of fuel required to refill the tank.
- Calculating MPG from partial fill-ups: If you add $20 of gas into a half-empty tank, you cannot calculate MPG because you do not know the ending fuel level.
- Non-linear fuel savings: Improving from 15 MPG to 20 MPG saves 167 gallons every 10,000 miles. Improving from 45 to 50 MPG saves only 22 gallons. Focus on gallons saved rather than raw MPG points.
Frequently Asked Questions
Learn step-by-step MPG formulas and real-world testing procedures.
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