How do I calculate the gas cost of a trip?

Divide the trip distance by your car's miles per gallon to get the gallons you will burn, then multiply that by the price per gallon. For a 300-mile trip in a 25 MPG car at $3.00 a gallon: 300 ÷ 25 = 12 gallons, and 12 × $3.00 = $36.

Should I enter one-way or round-trip miles?

Enter whichever you want the answer for. This tool shows both — a one-way figure and the round-trip cost — so entering the one-way distance is usually the simpler approach.

Where do the gas prices come from?

The U.S. Energy Information Administration, which publishes an average retail price survey every week. It is the same series used by federal agencies and most news coverage of pump prices. Prices are regional averages, so an individual station may be a few cents above or below.

Why is my actual fuel cost higher than the estimate?

Usually because real fuel economy falls short of the rated figure, or because the stations you used were above the state average. Highway speed, air conditioning, cargo weight, elevation gain, cold starts, and idling in traffic all reduce miles per gallon. Interstate and turnpike stations also tend to price above the surrounding area.

Does this work for electric vehicles?

Not directly. This calculator prices gallons of gasoline. An EV's cost per mile depends on your electricity rate and the vehicle's efficiency in kilowatt-hours per 100 miles, which is a different calculation from the one here.

Money & Economy

Gas Trip Cost Calculator

Enter your distance and fuel economy. Pump prices come from the weekly federal survey, so you only have to supply the parts we cannot know.

100 miles at 40 MPG costs about

$10.02

one way — or $20.03 round trip. That is 2.5 gallons at $4.006 a gallon (U.S. average).

Cost per mile: 10.0¢
Gallons needed: 2.5
Price per gallon: $4.006

The same trip at other fuel economies

MPG	Gallons	One-way cost
15	6.7	$26.71
20	5.0	$20.03
25	4.0	$16.02
30	3.3	$13.35
40	2.5	$10.02
50	2.0	$8.01

Pump prices from U.S. Energy Information Administration (EIA). Compare every state on the gas prices tracker.

Fuel cost for a drive is a three-number problem: how far you are going, how far your car goes on a gallon, and what a gallon costs where you are filling up. This tool supplies the third number from official weekly survey prices so you are not guessing at the pump rate.

Pick a state and the calculation uses that state's current average instead of the national one. That gap is not trivial — the spread between the cheapest and most expensive states is routinely more than a dollar a gallon, which is enough to change what a long drive costs by real money.

How the cost is calculated

Gallons used is trip distance divided by fuel economy, and cost is gallons multiplied by the price per gallon. A 600-mile drive in a car returning 30 miles per gallon burns 20 gallons; at $3.20 a gallon that is $64 one way. The arithmetic is simple, but the inputs are where estimates go wrong — see below.

Use your real MPG, not the sticker

The EPA combined figure on a window sticker is a laboratory average. Real-world economy is usually lower, and the gap widens with highway speed, roof boxes, heavy loads, cold weather, and aggressive driving. Sustained driving above roughly 60 miles per hour costs noticeable efficiency because aerodynamic drag rises with the square of speed. If your car has a lifetime average readout, that number will produce a better estimate than the sticker.

Why state prices differ so much

Two things drive most of the spread: taxes and logistics. Combined federal and state fuel taxes vary by more than 50 cents a gallon between the highest- and lowest-tax states, and some states require special cleaner-burning fuel blends that are refined and shipped separately. Distance from refineries and pipeline capacity account for much of the rest, which is why West Coast prices tend to sit above Gulf Coast prices regardless of tax policy.

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Gas Trip Cost Calculator — Frequently Asked Questions

How do I calculate the gas cost of a trip?: Divide the trip distance by your car's miles per gallon to get the gallons you will burn, then multiply that by the price per gallon. For a 300-mile trip in a 25 MPG car at $3.00 a gallon: 300 ÷ 25 = 12 gallons, and 12 × $3.00 = $36.
Should I enter one-way or round-trip miles?: Enter whichever you want the answer for. This tool shows both — a one-way figure and the round-trip cost — so entering the one-way distance is usually the simpler approach.
Where do the gas prices come from?: The U.S. Energy Information Administration, which publishes an average retail price survey every week. It is the same series used by federal agencies and most news coverage of pump prices. Prices are regional averages, so an individual station may be a few cents above or below.
Why is my actual fuel cost higher than the estimate?: Usually because real fuel economy falls short of the rated figure, or because the stations you used were above the state average. Highway speed, air conditioning, cargo weight, elevation gain, cold starts, and idling in traffic all reduce miles per gallon. Interstate and turnpike stations also tend to price above the surrounding area.
Does this work for electric vehicles?: Not directly. This calculator prices gallons of gasoline. An EV's cost per mile depends on your electricity rate and the vehicle's efficiency in kilowatt-hours per 100 miles, which is a different calculation from the one here.

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