acalculator

How much will gas cost?

Enter how far you are going, how far your car goes on a gallon or a litre, and the price of fuel. See how much fuel the trip uses and what it costs.

Your numbers

Units
Fuel cost
$44.78

Driving 250 mi uses 10 gal of fuel, which costs $44.78.

Fuel used
10 gal
Fuel used (litres)
37.9 L
Cost per person
$44.78
Distance driven
250 mi

Fuel cost: $44.78. Driving 250 mi uses 10 gal of fuel, which costs $44.78.

How to calculate

Computes the fuel a trip uses and what it costs from the distance, the fuel economy in mpg, L/100 km or km/L, and the price per gallon or litre, with a round trip and a split between people.

Example with the default inputs (Distance 250 mi, Round trip No, Fuel economy 25, Fuel economy unit mpg (US), Fuel price $4.48, Price per Gallon (US), Split between 1): Driving 250 mi uses 10 gal of fuel, which costs $44.78.

Method: fuel = distance ÷ fuel economy (or distance × L/100 km ÷ 100); cost = fuel × price per unit of fuel

  • The fuel economy is the car’s average for the trip. Speed, load, traffic and weather change it.
  • mpg is miles per US gallon (3.785411784 L). L/100 km and km/L are converted exactly.
  • The default price is the US average for regular gasoline in the week of September 21, 2026, from the EIA. Type your local price.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Distance 15,000 mi, Round trip no, Fuel economy 20, Fuel economy unit mpg (US), Fuel price $3.60, Price per Gallon (US), Split between 1 gives Fuel used 750 gal, Fuel cost $2,700.00.Source: fueleconomy.gov, Fuel Economy Savings Calculator (cited in content.mdx): 15,000 miles at 20 mpg and $3.60 a gallon; 15,000 ÷ 20 = 750 gal × $3.60 = $2,700 (hand calculation in content.mdx)
  2. Distance 15,000 mi, Round trip no, Fuel economy 30, Fuel economy unit mpg (US), Fuel price $3.60, Price per Gallon (US), Split between 1 gives Fuel used 500 gal, Fuel cost $1,800.00.Source: fueleconomy.gov, Fuel Economy Savings Calculator: the 30 mpg car costs $900 less a year than the 20 mpg car; 15,000 ÷ 30 = 500 gal × $3.60 = $1,800
  3. Distance 186.4 mi, Round trip yes, Fuel economy 7.5, Fuel economy unit L/100 km, Fuel price $1.80, Price per Litre, Split between 3 gives Fuel used 11.89 gal, Fuel cost $81.00, Cost per person $27.00.Source: hand calculation in content.mdx: 600 km × 7.5 ÷ 100 = 45 L; × $1.80 = $81; ÷ 3 = $27
  4. Distance 74.56 mi, Round trip no, Fuel economy 15, Fuel economy unit km/L, Fuel price $4.48, Price per Gallon (US), Split between 1 gives Fuel used 2.11 gal, Fuel cost $9.46.Source: hand calculation in content.mdx: 120 ÷ 15 = 8 L = 2.113 gal; × $4.478 = $9.46

How it works

  1. Distance driven = the one-way distance, times 2 for a round trip.
  2. Fuel used:
    • mpg (miles per US gallon): gallons = miles ÷ mpg.
    • L/100 km: litres = kilometres × L/100 km ÷ 100.
    • km/L: litres = kilometres ÷ km/L.
  3. Fuel cost = fuel used × price, with the fuel in the price's unit (US gallons or litres).
  4. Cost per person = fuel cost ÷ number of people.

Units convert exactly: 1 mile = 1.609344 km and 1 US gallon = 3.785411784 L.

The starting price is the EIA's US average for regular gasoline in the week of September 21, 2026: $4.478 a gallon.

Worked examples by hand

15,000 miles at 20 mpg and $3.60 a gallon (the fueleconomy.gov example). 15,000 ÷ 20 = 750 gallons. 750 × 3.60 = $2,700.

The same at 30 mpg. 15,000 ÷ 30 = 500 gallons, and 500 × 3.60 = $1,800, which is $900 less.

A 300 km trip, there and back, at 7.5 L/100 km and $1.80 a litre, split three ways. 300 × 2 = 600 km. 600 × 7.5 ÷ 100 = 45 L. 45 × 1.80 = $81, or $27 each.

120 km at 15 km/L, priced at $4.478 a US gallon. 120 ÷ 15 = 8 L. 8 ÷ 3.785411784 = 2.113 gal. 2.113 × 4.478 = $9.46.

Other questions people ask

How do I calculate the gas cost of a trip?

Divide the distance by your mpg to get gallons, then multiply by the price per gallon. 250 miles at 25 mpg is 10 gallons; at $4.478 a gallon that is $44.78.

How do I use L/100 km?

L/100 km is litres used per 100 kilometres. Fuel = distance in km × L/100 km ÷ 100. A 600 km round trip at 7.5 L/100 km uses 600 × 7.5 ÷ 100 = 45 L.

How much does better fuel economy save?

fueleconomy.gov shows that at 15,000 miles a year and $3.60 a gallon, a 30 mpg car costs $900 a year less to fuel than a 20 mpg car: 500 gallons ($1,800) against 750 gallons ($2,700).

What price does the calculator start with?

The US average retail price of regular gasoline for the week of September 21, 2026, $4.478 a gallon, from the U.S. Energy Information Administration. Prices change every week and differ by state, so type the price at your pump.

How do I split gas money with friends?

Enter how many people share the ride in Split between. The calculator divides the fuel cost equally. It does not add tolls, parking or wear on the car.

Why does my real fuel use differ?

Rated mpg is measured on set test cycles. Highway speed, air conditioning, a full load, cold weather and traffic all change it, so use the average your car shows for trips like this one if you have it.