How to Calculate Trip Fuel Cost

Step 1: Measure Your Trip Distance

The first thing you need is the total distance you'll travel. You can find this using:

• Map apps: Google Maps, Apple Maps, or Waze show distance when you enter your route
• GPS devices: Most car navigation systems display trip distance
• Odometer: Note your starting and ending readings
• Online route planners: Many websites calculate distances between cities

Make note of whether the distance is in kilometers or miles, as you'll need this later.

Step 2: Find Your Vehicle's Fuel Consumption

Your vehicle's fuel consumption (also called fuel economy or mileage) tells you how much fuel it uses. This is expressed in different ways depending on where you are:

• L/100km (Liters per 100 kilometers): Common in Europe, Australia, Canada. Example: 7.5 L/100km
• MPG (Miles Per Gallon): Used in US and UK. Example: 30 MPG (US) or 35 MPG (UK)
• km/L (Kilometers per Liter): Common in Asia and Latin America. Example: 13 km/L

Where to find this number:

• Owner's manual or manufacturer's website
• Vehicle's trip computer or dashboard display
• Calculate it yourself: fill your tank, drive normally, refill and divide distance by fuel added

Step 3: Check Current Fuel Prices

Look up the current price of fuel in your area. Prices are typically shown as:

• Price per liter (most countries)
• Price per gallon (US and UK)

Remember that US and UK gallons are different sizes. If you're traveling through multiple areas, you might want to use an average price or the highest price you expect to pay.

Step 4: Convert Units (If Needed)

For easier calculation, it helps to convert everything to a common system. The metric system (km, liters, L/100km) is often simplest:

• Miles to km: multiply by 1.609
• US gallons to liters: multiply by 3.785
• UK gallons to liters: multiply by 4.546
• MPG (US) to L/100km: divide 235.214 by MPG
• MPG (UK) to L/100km: divide 282.481 by MPG
• km/L to L/100km: divide 100 by km/L

Use our conversion tool if you need help with this step.

Step 5: Calculate Fuel Needed

Now you can calculate how much fuel you'll need for the trip.

Step 6: Calculate Total Cost

Finally, multiply the fuel needed by the price per liter to get your total cost.

Complete Worked Example

Scenario: You're driving from Chicago to Milwaukee. Your car's EPA rating is 28 MPG (US), and gas costs $3.50 per gallon.

1. Distance: Google Maps shows 92 miles
2. Consumption: 28 MPG (US)
3. Price: $3.50 per US gallon
4. Fuel needed: 92 miles ÷ 28 MPG = 3.29 gallons
5. Total cost: 3.29 × $3.50 = $11.51

Alternative Example (Metric)

Scenario: Driving 400 km in India. Your car gives 15 km/L, and petrol costs ₹105 per liter.

1. Distance: 400 km
2. Consumption: 15 km/L (convert: 100 ÷ 15 = 6.67 L/100km)
3. Price: ₹105 per liter
4. Fuel needed: 400 × 6.67 ÷ 100 = 26.67 liters
5. Total cost: 26.67 × ₹105 = ₹2,800

Tips for More Accurate Estimates

Use real-world consumption: Official ratings are often optimistic. If you know your actual average consumption from experience, use that instead.

Account for driving conditions: Highway driving is more efficient than city driving. If your trip is mostly highway, you might use 10-15% less fuel than the combined rating.

Consider external factors: Headwinds, hills, heavy loads, and cold weather all increase fuel consumption. In extreme conditions, add 10-20% to your estimate.

Check multiple fuel prices: Prices can vary significantly between stations and regions. Apps like GasBuddy help you find the cheapest fuel along your route.

What This Calculation Doesn't Include

This basic calculation covers fuel costs only. For a complete trip budget, also consider:

• Tolls and road fees
• Parking charges
• Vehicle wear and tear (tires, oil, maintenance)
• Food and accommodation if it's a long trip

Use Our Calculator

While it's useful to understand the math, our calculator does all these steps instantly. Just enter your distance, fuel price, and vehicle efficiency in any units, and get your answer in seconds.