Whether you're planning a cross-country road trip, splitting gas money with friends, or just calculating your daily commute expenses, the Fuel Cost Calculator provides an exact estimate of your transportation budget. It takes the guesswork out of travel planning by using precise fuel efficiency metrics and current local fuel prices.

Estimating fuel cost is essential not only for personal budgeting but also for businesses managing fleets or calculating reimbursement rates for employees.

The Fuel Cost Formula

Calculating fuel cost manually depends on the unit of measurement used in your region. In the US, the standard formula is based on MPG (Miles Per Gallon):

Total Cost = (Trip Distance / MPG) × Fuel Price per Gallon

For regions using the metric system (Liters per 100 Kilometers), the formula shifts:

Total Cost = (Trip Distance / 100) × L/100km × Price per Liter

International Unit Conversion

Different regions measure fuel economy differently. This calculator seamlessly translates between them behind the scenes:

1 US Gallon3.78541 Liters

1 Imperial (UK) Gallon4.54609 Liters

1 Mile1.60934 Kilometers

Factors Affecting Fuel Economy

Your vehicle's EPA-rated fuel efficiency is an estimate based on controlled laboratory testing. Real-world fuel economy can fluctuate by up to 20% or 30% depending on several dynamic variables.

Driving Habits & Speed

Rapid acceleration and hard braking can lower gas mileage by 15% to 30% at highway speeds and 10% to 40% in stop-and-go traffic. Additionally, fuel efficiency drastically drops at speeds above 50 MPH. Assuming a gallon of gas costs $3.50, every 5 MPH you drive over 50 is equivalent to paying an extra $0.25 per gallon.

Weight and Drag (Aerodynamics)

An extra 100 pounds in your vehicle can reduce your MPG by about 1%. Roof cargo boxes, bike racks, and even driving with the windows down at highway speeds increase aerodynamic drag significantly, which can decrease fuel economy by 2% to 15%.

Vehicle Maintenance

Keeping tires inflated to the proper pressure can improve your gas mileage by up to 3%. Using the manufacturer's recommended grade of motor oil can also improve fuel economy by 1% to 2%. Fixing a serious maintenance problem, such as a faulty oxygen sensor, can improve your mileage by up to 40%.

Idling & Air Conditioning

Idling can use a quarter to a half gallon of fuel per hour. Air conditioning also places a heavy load on the engine; running the AC in extremely hot weather can reduce a vehicle's fuel economy by more than 25%.

Disclaimer on Electric Vehicles (EVs)

While this calculator is optimized for Internal Combustion Engine (ICE) and hybrid vehicles running on liquid fuel, EV owners can calculate their "fuel" cost using our Electricity Cost Calculator by replacing the "gallon" metrics with kWh consumption data from their charging logs.

How the calculation works

Fuel cost is the gallons needed times the price per gallon.

Gallons = miles ÷ mpg Cost = gallons × price

In metric units, liters = kilometers × L/100km ÷ 100.

Worked example: 300 miles at 30 mpg and $3.50 per gallon

Gallons = 300 ÷ 30 = 10.
Cost = 10 × $3.50 = $35.

Cost of a 300-mile trip at $3.50 per gallon

MPG	Gallons	Cost
20	15.0	$52.50
30	10.0	$35.00
40	7.5	$26.25

Frequently asked questions

What does a 300-mile trip cost at 30 mpg and $3.50 a gallon?▼

$35.

How many gallons is that?▼

10.

What if the car gets 20 mpg?▼

15 gallons and $52.50.