Fuel Cost Calculator

How Fuel Cost Is Calculated

Trip fuel cost depends on three things: distance, fuel efficiency (how much fuel your vehicle uses per distance), and price per unit of fuel. The formula is simple: cost = (distance ÷ efficiency) × price when using MPG, or cost = (distance × efficiency ÷ 100) × price when using L/100km. Our calculator does this instantly and lets you add a round trip (double the distance) and an optional buffer so your estimate is closer to real-world spending.

MPG vs L/100km

MPG (miles per gallon) is common in the US and UK: higher is better (e.g. 35 MPG means 35 miles per gallon). L/100km (liters per 100 km) is used in Europe and elsewhere: lower is better (e.g. 7 L/100km means 7 liters to drive 100 km). To convert roughly: 235 ÷ MPG ≈ L/100km, and 235 ÷ L/100km ≈ MPG. This tool supports both; switch the unit and enter your car’s figure from the sticker or manual.

Real-World Examples

A 300-mile trip in a car that gets 30 MPG, with fuel at $3.50/gallon: fuel used = 300 ÷ 30 = 10 gallons; cost = 10 × 3.50 = $35. For a 500 km trip at 7 L/100km and €1.60 per liter: fuel = (500 ÷ 100) × 7 = 35 liters; cost = 35 × 1.60 = €56. Enabling “round trip” doubles the distance (and cost) for the return journey. Adding a 5% buffer increases the fuel amount (and cost) by 5% to account for traffic and conditions.

Budget Planning Tips

Use the calculator before a road trip to set a fuel budget. Check current fuel prices along your route if they vary by region. Add a buffer (e.g. 5–10%) so you’re not caught short. For recurring commutes, run the calculation once and multiply by your trips per month. Compare different vehicles by changing efficiency to see how much you’d save with a more efficient car. For more financial planning, try our hourly pay calculator or percentage calculator.

Why Estimates Vary

Sticker efficiency is measured under standard conditions. In real life, speed, traffic, load, air conditioning, and terrain all affect consumption. Short trips and cold starts often use more fuel per mile. That’s why we include an optional buffer and a clear note: estimates assume constant efficiency; actual cost may vary. Use the result as a planning guide, not a guarantee.

Trip Fuel Cost Calculator: What You Get

This fuel expense calculator gives you instant estimates for a single trip or round trip, in your preferred currency. You can switch between MPG and L/100km without changing your mental math—the tool handles the conversion. The optional consumption buffer (e.g. +5% or +10%) helps you plan for real-world driving so you don’t underestimate. A shareable link and copy-results button let you save or send your estimate. Everything runs in your browser; no data is sent to any server, so your trip details stay private.

Finding Your Car’s Efficiency

Your vehicle’s fuel economy is usually on the window sticker (EPA in the US, or the equivalent in your country) or in the owner’s manual. If you track fill-ups and distance, you can compute it yourself: divide miles driven by gallons used for MPG, or (liters used × 100) ÷ km driven for L/100km. Using a measured average is more accurate than the sticker for your own driving style. Once you have the number, plug it into the gas cost estimator along with your trip distance and local fuel price to get your estimated cost.

Efficiency Comparison Tips

To compare vehicles or driving scenarios, run the calculator twice with different efficiency values and the same distance and fuel price. A car that gets 40 MPG instead of 25 MPG uses 37.5% less fuel on the same trip—so the cost difference is substantial on long journeys. Use the round-trip option when planning return travel, and add a small buffer (5–10%) so your fuel budget stays realistic. For more budgeting tools, see our percentage calculator or hourly pay calculator.