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Gas Mileage Calculator Guide
Your car's real-world fuel economy is often different from the sticker. This calculator works out your actual miles per gallon (and the metric equivalents) from the distance you drove and the fuel it took to refill.
MPG = miles driven ÷ gallons used. To convert: L/100km = 235.2 ÷ MPG, and km/L = MPG × 0.425.
How Do I Calculate Gas Mileage?
Fill your tank and reset the trip odometer. Drive normally, then refill and note the miles driven and gallons added. Divide the miles by the gallons to get your MPG for that tank — repeat over a few tanks for a reliable average.
Worked Example
Drove 320 miles and refilled with 10 gallons: MPG = 320 ÷ 10 = 32 MPG, which is about 7.4 L/100km or 13.6 km/L.
Tips for Accurate Readings
- Fill to the same click each time so the starting and ending levels match.
- Average several tanks — a single tank varies with driving and conditions.
- Note city vs highway driving, which changes economy significantly.
Turn your MPG into a trip budget with the Fuel Cost Calculator, and check tire effects with the Tire Size Calculator.
Frequently Asked Questions
How do I calculate gas mileage?
Divide the miles you drove by the gallons of fuel it took to refill the tank.
What is good gas mileage?
Many modern cars average 25–35 MPG, hybrids often 45–55 MPG, though it depends on the vehicle and driving.
How do I convert MPG to L/100km?
Divide 235.2 by your MPG — for example, 32 MPG is about 7.4 L/100km.
Why is my real MPG lower than the sticker?
City driving, cold weather, short trips, and aggressive driving all lower real-world economy below the rated figure.
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