onlinecalculator.me

Free online fuel cost calculator

Fuel cost is distance divided by efficiency, multiplied by the price per unit. This calculator handles both MPG (US) and L/100km (metric) so you can price any road trip or daily.

Total fuel cost
$—
Fuel used
— gal
Cost per mile
$—
About this calculator

How to use

  1. Toggle MPG or L/100km to match how your car’s efficiency is rated.
  2. Enter the trip distance in miles or kilometers.
  3. Enter your car’s fuel efficiency (MPG or L/100km).
  4. Enter the current gas or diesel price per gallon or liter.
  5. Read total cost, fuel used, and cost per mile or per kilometer.

Formulas

MPG mode:

fuel used (gal) = distance (mi) ÷ MPG
total cost      = fuel used × price per gallon
cost per mile   = price per gallon ÷ MPG

L/100km mode:

fuel used (L) = (distance (km) ÷ 100) × L/100km
total cost    = fuel used × price per liter
cost per km   = (L/100km ÷ 100) × price per liter

Worked examples

US road trip: 300 miles at 30 MPG, gas at $3.50/gallon:

fuel used  = 300 ÷ 30      = 10 gallons
total cost = 10 × 3.50     = $35.00
cost/mile  = 3.50 ÷ 30     = $0.12

European drive: 500 km at 7 L/100km, fuel at €1.75/liter:

fuel used  = (500 ÷ 100) × 7 = 35 liters
total cost = 35 × 1.75       = €61.25
cost/km    = (7 ÷ 100) × 1.75 = €0.1225

Notes

  • Actual fuel economy is usually 10–20% lower than EPA/WLTP ratings in real-world driving.
  • Highway driving is more efficient than city driving for most non-hybrid vehicles.
  • For electric vehicles, substitute kWh/100mi or mi/kWh and price per kWh for a comparable cost estimate.

Frequently asked

How do I calculate fuel cost for a road trip?
Fuel cost = (distance ÷ MPG) × price per gallon. For example, a 300-mile trip at 30 MPG with gas at $3.50/gal costs (300 ÷ 30) × 3.50 = $35.00. The calculator shows this instantly.
How do I convert MPG to L/100km?
L/100km = 235.21 ÷ MPG. So 30 MPG is about 7.84 L/100km. Switch the unit toggle at the top and enter your metric values directly — no manual conversion needed.
What is a good MPG for a car?
For a non-electric passenger car: under 25 MPG is below average, 25–35 MPG is average, 35–50 MPG is efficient (hybrids), and 50+ MPG is hybrid or plug-in hybrid territory. EPA fuel economy labels list combined city/highway MPG.
How does the L/100km mode work?
In L/100km mode, fuel used = (distance in km ÷ 100) × L/100km value. A 500 km trip at 9 L/100km uses 45 liters. Cost = 45 × price per liter.
What is cost per mile and why is it useful?
Cost per mile = price per gallon ÷ MPG. It lets you compare vehicles with different fuel efficiencies on an equal footing. At $3.50/gal and 30 MPG, you pay about $0.12 per mile.

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