Fuel Cost Calculator
Estimate how much fuel a trip needs and what it costs, per trip, per month and per year, in US or metric units.
Fuel Cost Calculator — input your values
What does this everyday calculator do?
The fuel cost calculator converts a trip distance and a fuel efficiency rating into the amount of fuel burned and the money spent, using either US units (miles, miles per gallon, dollars per gallon) or metric units (kilometers, liters per 100 km, dollars per liter).
When you enter how many times the trip happens per month, it also reports monthly and yearly fuel use and cost, which is handy for commuting budgets and road-trip planning.
Formula and variables
In metric units, liters per 100 km is divided by 100 so the fuel figure scales with distance linearly.
| Symbol | Meaning |
|---|---|
| Fuel per trip | Gallons or liters used on one trip |
| Cost per trip | fuel per trip × fuel price |
| Monthly cost | cost per trip × trips per month |
Worked example
A 120-mile commute at 30 MPG with gas at $3.50 per gallon, driven 20 times a month.
- Fuel per trip = 120 ÷ 30 = 4 gallons.
- Cost per trip = 4 × $3.50 = $14.00.
- Monthly cost = $14.00 × 20 = $280.00.
- Annual cost = $280.00 × 12 = $3,360.00.
Answer: The commute costs $14.00 per trip and $3,360.00 per year.
Tips and common mistakes
Tips
- For commutes, count trips per month as the number of round trips — a daily 20-mile commute is 40 miles and 20 round trips a month.
- Use the highway MPG for long drives and the city figure for stop-and-go traffic to get a more accurate estimate.
- Electric vehicles can be compared by substituting the price per kWh and efficiency in kWh per 100 miles.
- If the price is per liter but the distance is in miles, switch both inputs to the same unit system to stay consistent.
Common mistakes to avoid
- Mixing unit systems, such as using miles with liters per 100 km, which corrupts the fuel figure.
- Entering the distance of one leg when the trip is a round trip, halving the true fuel use.
- Using the manufacturer's ideal MPG instead of the real-world figure from your trip computer or receipts.
Fuel Cost Calculator — frequently asked questions
How do I calculate fuel cost for a trip?
Divide the distance by your fuel efficiency to get the fuel needed, then multiply by the fuel price. 100 miles at 25 MPG and $3.50 per gallon costs $14.00.
What is the difference between MPG and L/100km?
MPG is miles per gallon — higher is better. L/100km is liters per 100 kilometers — lower is better. The calculator accepts either system.
How much gas does a trip use?
Distance divided by efficiency. A 300-mile trip in a car that gets 30 MPG uses 10 gallons, about 37.9 liters.
Why is my actual fuel use higher than the estimate?
City traffic, cold weather, air conditioning, roof racks and aggressive driving all reduce efficiency, sometimes by 20% to 30%.
How do I estimate my annual fuel budget?
Add up the trips you take each month, find the monthly cost, and multiply by 12. The calculator does this when you enter trips per month.
Can I use this for diesel, hybrids or EVs?
Yes. Enter any fuel price and efficiency figure. For EVs, use efficiency in kWh per 100 miles (or km) and the price per kWh as the fuel price.