How Fuel Cost Is Calculated

It's a two-step calculation:

Gallons needed: distance ÷ MPG
Total cost: gallons × price per gallon

For example, a 300-mile trip in a car getting 28 MPG at $3.50/gal needs about 10.7 gallons and costs about $37.50.

Example Costs for a 300-Mile Trip

Fuel Economy	Gallons Used	Cost @ $3.50/gal
20 MPG	15.0	$52.50
25 MPG	12.0	$42.00
28 MPG	10.7	$37.50
32 MPG	9.4	$32.81
40 MPG	7.5	$26.25

Key takeaway: The difference between 20 MPG and 40 MPG on this trip is about $26. Over many miles, fuel economy is one of the biggest ongoing costs of owning a car.

Ways to Reduce Fuel Cost

Drive steady: Aggressive acceleration and braking can cut MPG by 10–40% in city driving.
Keep tires inflated: Properly inflated tires improve fuel economy and last longer.
Lighten the load: Extra weight (and roof racks) increase fuel use.
Use cruise control on highways: Steady speed is more efficient.
Reduce idling: Turn the engine off during long waits; idling burns fuel with zero miles.
Shop around: Gas prices can vary significantly even between nearby stations.

Frequently Asked Questions

What is MPG and how do I find mine?

MPG stands for "miles per gallon" — how many miles you can drive on one gallon of fuel. Find yours by noting the odometer at a full tank, then dividing miles driven by gallons added at the next fill-up.

Does highway vs. city driving change the cost?

Yes. Highway driving is usually more efficient than stop-and-go city driving, so your real MPG varies by route. Use your typical number for the kind of driving you'll do.

What if I use liters and kilometers?

This calculator uses miles and gallons (common in the U.S.). You can convert: 1 gallon ≈ 3.785 liters, and 1 mile ≈ 1.609 km. For a liters-per-100km approach, the math is slightly different.

Fuel Cost Calculator