MPG & Fuel Efficiency Calculator
Calculate MPG from miles driven and fuel used, estimate trip fuel costs, determine driving range, or convert between MPG and L/100km.
MPG Calculator
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The Formula
Miles per gallon (MPG) is the US standard fuel efficiency measure. The conversion factor 235.215 converts between MPG and liters per 100 km (the metric standard). Lower L/100km is better fuel economy.
Variable Definitions
Miles Per Gallon
Number of miles a vehicle can travel on one gallon of fuel. Higher MPG = better fuel economy. The US standard measure of fuel efficiency.
Liters per 100 Kilometers
Metric standard measure of fuel consumption. Lower values are better. A car that gets 30 MPG consumes about 7.8 L/100km.
Kilometers per Liter
Metric measure of fuel economy. 1 MPG ≈ 0.425 KPL. Used in countries like Canada, the UK, and Japan.
How to Use This Calculator
- 1
Select the calculation type from the dropdown: MPG, trip cost, range, or unit conversion.
- 2
Enter the required values for your selected calculation.
- 3
View fuel economy, trip costs, or unit conversions.
- 4
Use the range mode to estimate how far you can drive on a full tank (with a 10% reserve).
Common Applications
- Measuring your vehicle actual fuel economy by tracking miles driven and gallons used between fill-ups
- Estimating fuel cost for an upcoming road trip using your car real MPG and current gas prices
- Calculating how far you can drive on a full tank to plan long-distance routes and fuel stops
- Converting between MPG and L/100km when comparing US and international vehicle fuel efficiency ratings
MPG scale — higher bars represent better fuel efficiency
Understanding the Concept
Fuel economy is measured in MPG in the United States and most of the Western hemisphere. Europe and most of the world use L/100km (lower is better). To convert: L/100km = 235.215 ÷ MPG. The EPA tests vehicles under standardized conditions — real-world MPG is typically 10-20% lower. Factors affecting real-world MPG include driving speed (every 5 mph over 50 mph is like paying $0.18-$0.30 more per gallon), air conditioning use (can reduce MPG by up to 25% in extreme conditions), tire pressure (under-inflated tires can lower MPG by 0.3% per 1 PSI drop), cargo weight (every 100 pounds reduces MPG by about 1-2%), and road grade (hilly terrain significantly increases fuel consumption). For hybrid and electric vehicles, driving style has an even larger impact — aggressive acceleration can reduce efficiency by 30-40% compared to smooth driving. The trip cost mode helps you budget for road trips: a 1,000 mile trip in a car getting 30 MPG at $3.50 per gallon costs about $117 in fuel. The range mode answers the common question "how far can I go on a tank?" — a 15-gallon tank at 30 MPG gives 450 miles of range, or about 405 miles of practical range leaving a 10% reserve.
Frequently Asked Questions
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