Fuel Cost Calculator
Calculate trip fuel cost from distance and efficiency, in mpg or L/100km, with unit conversion.
Written by Golam Rabbani, Founder & Lead Engineer
How to use this fuel cost calculator
- Choose unit system: "Miles & mpg" or "km & L/100km".
- Enter your trip distance.
- Enter your vehicle's fuel efficiency in the chosen units.
- Enter the fuel price per gallon (or per litre).
- Press Calculate to see total fuel cost, fuel used, and cost per mile or km.
About this fuel cost calculator
The fuel cost calculator estimates how much a trip will cost in fuel from three numbers: distance, your vehicle's efficiency, and the price at the pump. It handles both unit systems used worldwide — US-style miles per gallon (where higher is better) and the metric L/100km figure used in most other countries (where lower is better). Switching systems converts values automatically so you do not have to retype.
Worked example: a 350-mile road trip in a car rated 28 mpg with gas at $3.50/gallon. Gallons used = 350 ÷ 28 = 12.5 gallons. Total cost = 12.5 × $3.50 = $43.75, or about $0.125 per mile. The same trip in metric: 563 km, 8.4 L/100 km, $1.65/litre → 47.3 L × $1.65 ≈ $78.05 (different fuel prices give a different total, of course).
Use it to budget a road trip, compare two routes, or check whether a hybrid will pay for itself. All math runs in the browser; nothing is uploaded.
FAQ
- How do I convert mpg to L/100km?
- L/100km = 235.214583 ÷ mpg. So 30 mpg ≈ 7.84 L/100km. The unit toggle in the calculator does this conversion for you automatically when you switch.
- Which fuel efficiency should I use — highway, city, or combined?
- Use the figure that best matches the trip. For mostly-highway driving use the highway number; for stop-and-go use city; for mixed driving use combined. Real-world results vary with terrain, load, speed, and weather.
- Does the tool handle electric or hybrid vehicles?
- It is built for fuel-burning vehicles where efficiency is mpg or L/100km. For an EV, you would need to use kWh/100mi and $/kWh — different units the tool does not support.
- What if my fuel price is in a different currency?
- The calculator just multiplies — it treats the price input as a number and labels the result in dollars. The math is identical whether you read it as USD, GBP, or EUR per gallon/litre.
- Is the calculator free?
- Yes. It is free, runs entirely in your browser, requires no signup, and never sends your inputs anywhere.