Gas Mileage Calculator — Calculate MPG and Fuel Costs

Miles DrivenEnter valid miles.

Gallons of Fuel UsedEnter a valid amount.

Gas Price per Gallon ($, optional)

Fuel Efficiency

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Cost per Mile

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How to Use This Tool

Enter the miles driven and gallons of fuel used for a tank or trip.
Optionally enter the gas price to see your cost per mile.
Click Calculate for your fuel efficiency.

The MPG Formula

MPG = Miles Driven ÷ Gallons of Fuel Used

Cost per Mile = Gas Price per Gallon ÷ MPG

Getting an Accurate Reading

For the most accurate MPG calculation, fill your tank completely, reset your trip odometer, drive normally until you need to refuel, then fill up again completely and note the gallons required and miles driven since your last fill-up.

Why MPG Varies

Driving style: Aggressive acceleration and braking reduces efficiency significantly
Speed: Fuel efficiency typically peaks around 50-60 mph and drops at higher highway speeds due to increased aerodynamic drag
City vs. highway: Stop-and-go city driving typically yields lower MPG than steady highway cruising
Vehicle maintenance: Under-inflated tires, dirty air filters, and overdue maintenance all reduce efficiency
Weather and load: Cold weather, cargo weight, and using air conditioning all reduce MPG

Frequently Asked Questions

How do I get the most accurate MPG measurement?

Fill your tank completely, reset your trip odometer, drive until your next fill-up, then divide the miles driven by the gallons needed to refill completely — doing this over several tanks gives a more reliable average.

Why is my actual MPG lower than the EPA rating on my car?

EPA ratings are measured under standardized test conditions that often don't match real-world driving — aggressive driving, cold weather, city traffic, and cargo load can all reduce real-world MPG below the official rating.

This calculator is provided for general informational and estimation purposes only. Results should not be treated as professional financial, tax, legal, medical, or engineering advice. Always verify critical calculations with a qualified professional or official source before making decisions.