BCBetter Calculators

Gas Mileage Calculator

Calculate your car's fuel efficiency in miles per gallon.

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Enter your values and click Calculate

How It Works

The gas mileage calculator uses a single formula: MPG = Miles Driven ÷ Gallons Used. MPG, or miles per gallon, is the standard US measure of fuel efficiency — it expresses how far your vehicle travels on one gallon of fuel. To get an accurate measurement, fill your tank completely and record your odometer reading. Drive your normal mix of city and highway miles, then fill up again and note exactly how many gallons it took to top the tank off. The miles driven is the difference between the two odometer readings; the gallons used is the amount needed to return the tank to full. The formula does not separate city from highway mileage — the result reflects your actual blended driving conditions. City driving typically yields lower MPG because of frequent stops, acceleration, and idle time, while steady highway cruising at consistent speed is more fuel-efficient. Comparing your calculated MPG against the EPA's stated estimate for your make, model, and year reveals how efficiently your vehicle is actually running. A sustained 10–15% drop below the EPA rating is a meaningful signal that can indicate under-inflated tires, a clogged air filter, worn spark plugs, or a failing oxygen sensor. Tracking your MPG across several consecutive fill-ups produces a reliable trend that a single measurement cannot provide.

Examples

Average Commuter
A typical weekly commute covering 300 miles on 12 gallons of fuel.
Result: MPG = 300 ÷ 12 = 25.00 MPG.
Highway Road Trip
A long highway trip covering 500 miles using 18 gallons.
Result: MPG = 500 ÷ 18 = 27.78 MPG.
City Driving
Stop-and-go urban driving over 220 miles consuming 11 gallons — illustrating the efficiency penalty of city conditions.
Result: MPG = 220 ÷ 11 = 20.00 MPG, reflecting the lower efficiency typical of urban driving.

Frequently Asked Questions

What is good gas mileage?
For non-hybrid gasoline vehicles, 30 MPG or higher is generally considered fuel-efficient. Most modern cars average 25–35 MPG on the highway and 18–25 MPG in city driving. Hybrid vehicles typically achieve 40–55 MPG combined, while electric vehicles are rated in MPGe (miles per gallon equivalent) rather than traditional MPG.
How do I measure gallons used accurately?
Start with a completely full tank and record your odometer reading. After your trip, fill the tank to full again and note exactly how many gallons it took to refill. The gallons-to-full figure is your fuel consumed, and the odometer difference is your miles driven — divide the two for your precise MPG reading.
Can I calculate L/100km with this?
Not directly, but the conversion is straightforward: L/100km = 235.2 ÷ MPG. For example, a vehicle achieving 30 MPG is equivalent to approximately 7.84 L/100km. Fuel consumption expressed in L/100km is the standard measure in most countries outside the United States.

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