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Calculator Answers

Gas Calculator

Blake Boege
Written by Blake Boege · Founder, Calculator Answers

A gas calculator is a fuel cost estimation tool that determines how much a trip will cost in fuel. It divides the trip distance by the vehicle's fuel efficiency to find the gallons of fuel required, then multiplies by the price per gallon to calculate the total cost. Drivers use it to budget road trips, split fuel costs among passengers, and compare the running cost of different vehicles.

Enter your trip distance, vehicle fuel efficiency (MPG), and gas price. We compute the total fuel cost, gallons of gas needed, and the cost split per passenger.

See also: Fuel Economy Converter, Combined Gas Law Calculator, and Ideal Gas Law Calculator.

Quick Answer

Calculate the fuel cost of a trip. Enter trip distance, your car's MPG, and the price per gallon to get total gas cost, gallons needed, round-trip cost, and cost split per person.

mi
MPG
$/gal
people

Keep as 1 if driving alone.

Fuel Cost Estimate

Total fuel cost

$14.00

4 gallons used

Total distance100 miles
Total gallons4 gal
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Examples

300 mi trip · 30 MPG · $3.50/gal

10 gal · $35.00

150 mi trip · 20 MPG · $4.20/gal

7.5 gal · $31.50

1000 mi trip · 35 MPG · $3.50/gal

≈ 28.57 gal · $100.00

How it works

Fuel needed is calculated by dividing distance by fuel efficiency (MPG). Total cost is the fuel volume multiplied by the price of gas per gallon. Cost per person splits that total cost evenly among the number of passengers.

Gallons · Distance ÷ MPG = gal

Total Cost · Gallons × Price = Cost

Fuel Cost per 100 Miles lookup table

Below is a handy lookup table showing the estimated fuel cost to drive 100 miles at different vehicle MPG ratings, assuming a sample gas price of $3.50 per gallon:

Fuel Efficiency (MPG)Gallons per 100 MilesCost per 100 Miles (at $3.50/gal)
15 MPG (SUV/Truck)6.67 gal$23.33
20 MPG (Crossover)5.00 gal$17.50
25 MPG (Sedan)4.00 gal$14.00
30 MPG (Compact Car)3.33 gal$11.67
35 MPG (Hybrid Car)2.86 gal$10.00
40 MPG (Efficient Hybrid)2.50 gal$8.75

Worked example of fuel calculation

Let's calculate the fuel cost for a road trip from Chicago to Indianapolis:

Trip Specs

One-way distance of 180 miles in a car that averages 30 MPG, with gas priced at $3.60/gallon.

  • Calculate gallons used: 180 miles ÷ 30 MPG = 6 gallons of gas
  • Calculate total cost: 6 gallons × $3.60/gal = $21.60
  • If splitting with 2 passengers (3 people total): $21.60 ÷ 3 = $7.20 per person

    • Related conversion and distance tools

    Fuel Economy ConverterKM to Miles Converter

    Sources: U.S. EPA fuel economy figures and highway driving statistics. Last reviewed: June 2026.

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    Frequently asked questions

    To calculate the gas cost, divide the total trip distance (in miles) by your vehicle's fuel efficiency (in MPG) to find the number of gallons needed. Then, multiply the gallons by the price of gas per gallon.

    It depends on your vehicle's fuel efficiency. For example, if your car gets 30 MPG, you will use exactly 10 gallons of gas (300 miles ÷ 30 MPG = 10 gallons). If gas costs $3.50 per gallon, the trip will cost $35.00.

    To split gas money, calculate the total fuel cost for the trip and divide it by the number of people sharing the cost. For instance, if a road trip costs $60.00 in gas and there are 3 passengers, each person owes $20.00.

    Yes, using the air conditioner can reduce a vehicle's fuel efficiency by 5% to 25%, depending on the outside temperature and driving conditions, as the AC compressor draws power from the engine.

    Yes, gas mileage typically decreases rapidly at speeds above 50 mph due to increased aerodynamic drag. Driving at 65 mph instead of 55 mph can reduce fuel efficiency by up to 10% to 15%.

    You can improve fuel efficiency by maintaining steady highway speeds, keeping tires inflated to the recommended pressure, avoiding carrying excess weight, and reducing aggressive acceleration and braking.

    MPG (Miles Per Gallon) measures how far you can drive on a single gallon of fuel (higher is better). L/100 km (Liters per 100 Kilometers) measures how many liters of fuel are needed to drive 100 kilometers (lower is better). If you need to convert between these units, use our dedicated converter.

    A round-trip calculation doubles the one-way distance between your starting point and destination, which in turn doubles the estimated fuel consumption and total cost.