Fuel Cost Calculator
It calculates the fuel cost of a trip from distance, vehicle efficiency and fuel price, and splits it between passengers.
Total fuel cost
$58.33
Per person
$29.17
Cost per mile
$0.117
Fuel used
16.7 gal
Total distance
500 miles
Cost per 100
$11.67
Monthly (20 trips)
$1,167
What it calculates
It calculates the fuel cost of a trip from distance, vehicle efficiency and fuel price, and splits it between passengers.
Why it matters
Fuel is usually the largest variable cost of driving, and it is the number people most often guess at.
Who it's for
Commuters, road trippers, rideshare drivers and anyone budgeting mileage.
Formula
- d
- Trip distance
- e
- Efficiency (MPG or L/100 km)
- p
- Fuel price per unit
Worked example
420 miles at 38 MPG, $3.60/gallon
- 1Fuel used = 420 ÷ 38 = 11.05 gallons
- 2Cost = 11.05 × 3.60
About $39.79, or $9.95 each between four people
How the fuel cost calculator works
Cost = (distance ÷ efficiency) × price for MPG, or (distance ÷ 100 × L/100 km) × price for metric. Real-world efficiency is typically below the official figure.
Pick the efficiency system your car uses. In MPG mode the price is per gallon and the distance in miles; in L/100km mode the price is per liter and the distance in kilometers.
Real-world consumption is usually 10–20% worse than the manufacturer figure, and motorway speeds above 110 km/h raise it further.
Common mistakes
- Using the manufacturer's optimiztic MPG rather than your observed figure.
- Forgetting the return leg.
- Ignoring that motorway speed, load and air conditioning all cut efficiency.
Tips and best practice
- Track two or three full tanks to get your real efficiency.
- Steady speeds around 55–65 mph are usually the most economical.
Frequently asked questions
How do I calculate fuel cost for a trip?
Divide distance by fuel efficiency to get fuel used, then multiply by the price per gallon or liter.
How do I convert MPG to L/100 km?
L/100 km = 235.215 ÷ MPG for US gallons, or 282.481 ÷ MPG for imperial. The scales run in opposite directions: higher MPG is better, lower L/100 km is better.
Does the calculator handle a return trip?
Enter the total distance you will drive, including the return leg.
How do I convert MPG to L/100km?
Divide 235.215 by the MPG figure for US gallons. 30 US MPG is about 7.8 L/100km. Note that the two scales run in opposite directions — higher MPG is better, lower L/100km is better.
Why is my real fuel economy worse than the official figure?
Official figures come from standardized test cycles. Real-world consumption is typically 10–20% higher, and motorway speeds above 110 km/h push it higher still.
Should I use US or imperial MPG?
Check which your car reports. Imperial MPG figures are about 20% higher than US ones for identical consumption, because the imperial gallon is larger.
Related calculators
Methodology & trust
- Formula source
- Standard fuel consumption arithmetic.
- Last updated
- 2026-07-28
- Privacy
- Every calculation runs in your browser. No inputs are sent to a server or stored.
- Accessibility
- Keyboard navigable, labeled inputs and WCAG AA color contrast.