Gas Mileage CalculatorFree online other calculator — instant results, no sign-up
Fuel economy from distance and fuel used.
About the Gas Mileage Calculator
The Gas Mileage Calculator computes vehicle fuel efficiency based on the distance driven and the volume of fuel consumed. It provides results in both US miles per gallon (MPG) and metric liters per 100 kilometers (L/100km). Drivers and fleet operators use it to monitor vehicle performance, track fuel consumption trends, and calculate travel efficiency.
- Distance driven
- The total distance traveled on a given amount of fuel, measured in miles. Typically between 50 and 600 miles for standard vehicle tanks.
- Fuel used
- The total volume of fuel consumed over that distance, measured in US gallons. Typically between 1 and 30 gallons.
Formula and method
MPG = d / g L/100km = 235.215 / MPG = 235.215 / (d / g)
- dDistance driven in miles
- gFuel used in US gallons
- MPGMiles per US gallon
- L/100kmLiters consumed per 100 kilometers
Miles per gallon is determined by dividing total miles driven by gallons of fuel used. The calculator then converts MPG to liters per 100 kilometers by dividing the constant 235.215 by the calculated MPG value. Both results are rounded to two decimal places.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Distance driven350 miles
- Fuel used11 gal
Results
- MPG31.82
- L/100km7.39
How to use the Gas Mileage Calculator
- 1Enter the total distance driven in miles since the last fill-up.
- 2Enter the exact volume of fuel consumed in US gallons.
- 3Divide miles by gallons to get miles per gallon (MPG).
- 4Divide the standard conversion constant 235.215 by the resulting MPG to compute L/100km.
Reading your result
A higher MPG indicates better fuel economy, meaning you travel further on each gallon. Conversely, a lower L/100km rating indicates higher efficiency, representing fewer liters burned to cover 100 kilometers. Compare these numbers against your vehicle's factory ratings to evaluate driving habits or mechanical condition.
Limitations
The calculation reflects average fuel economy over the recorded period and does not separate highway from city driving. It assumes standard US liquid gallons rather than Imperial gallons. It also relies on accurate fuel measurement, which can vary depending on fuel pump auto-shutoff points.
Common questions
How do I accurately measure the fuel used for a trip?+
Fill your fuel tank completely, reset your trip odometer to zero, drive normally, and then fill the tank completely again. The number of gallons pumped during the second fill-up is your fuel used, and the trip odometer displays your distance driven.
Why is the conversion factor 235.215 used for L/100km?+
The factor 235.215 is derived from converting US gallons to liters (3.78541 L) and miles to kilometers (1.60934 km). Because L/100km is an inverse metric (volume over distance), dividing 235.215 by MPG provides the exact equivalent.
Does this calculator use US gallons or Imperial gallons?+
It uses US liquid gallons (approximately 3.785 liters). If you are using Imperial gallons (approximately 4.546 liters), the MPG and L/100km values will differ.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
Further reading
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Results are estimates for informational purposes and are not financial, medical or legal advice.