Fuel Cost Calculator

1. Pick US (miles, mpg, price per gallon) or metric (kilometres, litres per 100 km, price per litre).
2. Enter the distance, your fuel economy and the fuel price.
3. Read the total cost, the fuel used and the cost per mile or kilometre, all updating live.

Each output answers a different question:

Fuel cost is simply the price of the fuel a journey burns, and it depends on three things: how far you travel, how efficiently your vehicle uses fuel, and what the fuel costs per unit. Change any one and the total moves, which is why a long trip in a thirsty vehicle at a high pump price can cost several times more than a short, efficient one.

The tricky part is that economy is measured differently around the world. The United States uses miles per gallon, where higher is better, while most other countries use litres per 100 kilometres, where lower is better. This calculator handles both so you never have to convert by hand.

It works out how much fuel the distance needs, then multiplies that by the price per unit.

In US units, dividing the miles by the miles-per-gallon gives the gallons burned. In metric units, litres per 100 kilometres is multiplied by the distance and divided by 100 to give litres. Either way, the fuel used is then multiplied by the price to get the cost.

1. Turn distance and economy into the fuel used.
2. Multiply the fuel used by the price per gallon or litre.
3. Divide the cost by the distance for the cost per mile or kilometre.

Because economy is defined in opposite directions across the two systems, the calculator uses a different step for each rather than converting between them.

Drive 300 miles in a car that does 30 miles per gallon, with fuel at 3.50 a gallon. The gallons used are 300 / 30 = 10, so the cost is 10 x 3.50 = 35, about 11.7 cents per mile.

Switch to metric for a 480-kilometre trip at 8 litres per 100 kilometres and 1.50 a litre. The litres used are 480 x 8 / 100 = 38.4, and the cost is 38.4 x 1.50 = 57.60, or 12 cents per kilometre.

Improve the US car to 40 miles per gallon and the same 300-mile trip drops to 7.5 gallons and about 26.25, showing how strongly economy drives the bill.

These rough bands help you judge a vehicle economy before you enter it.

Notice the two scales move in opposite directions: a higher mpg is better, while a lower litres-per-100km figure is better. To turn a saving into a percentage, the percentage calculator helps.

The three inputs set the total, but real-world driving nudges the fuel used up or down.

Driving Style

Hard acceleration and high speeds burn far more fuel than smooth, steady driving, sometimes by a fifth or more.

Load and Terrain

A heavy load, roof box or hilly route all raise consumption above the vehicle rated economy.

Traffic and Weather

Stop-start traffic, cold starts and strong headwinds each cut economy, so a rated figure is a best case.

Fuel Price Swings

Pump prices move daily and by region, so the same trip can cost noticeably more or less week to week.

Planning a Road Trip

Estimate the fuel budget before you set off, and compare a direct route with a scenic one.

Comparing Vehicles

See how much a more efficient car would save over a typical year of driving before you buy.

Splitting Costs

Work out a fair share for passengers by turning the trip into a clear per-mile or per-kilometre figure.

1. Mixing US and Metric Figures

Keep distance, economy and price in the same system. Miles per gallon does not pair with a price per litre.

2. Using the Rated Economy as Exact

Official figures are a guide; real driving usually uses a little more fuel.

3. Forgetting the Return Leg

Enter the round-trip distance if you are coming back, not just the one-way figure.

4. Ignoring Price Differences

Fuel can be much cheaper a few miles away, so use a realistic local price.

5. Confusing L/100km with Km/L

Litres per 100 kilometres falls as efficiency rises; do not treat it like miles per gallon.

The arithmetic is exact for the figures you enter, but those figures are estimates of a changing real world.

Work out the fuel used, then multiply by the price. In US units, gallons = distance / mpg; in metric, litres = distance x economy / 100. This calculator does both.

At 30 miles per gallon and 3.50 a gallon, 100 miles uses about 3.33 gallons and costs around 11.67. Enter your own economy and price for an exact figure.

Miles per gallon measures distance per unit of fuel, so higher is better. Litres per 100 kilometres measures fuel per distance, so lower is better. They move in opposite directions.

Divide 235.2 by the miles-per-gallon figure. So 30 mpg is about 7.84 litres per 100 kilometres. This calculator avoids the conversion by handling each system directly.

Rated economy is a best case. Traffic, hills, load, cold weather and hard driving all raise consumption, so real trips often use a little more fuel.

Use whichever matches your journey. If you are returning, enter the full round-trip distance so the cost covers both legs.

Drive smoothly at steady speeds, keep tyres inflated, remove heavy loads and roof boxes, and buy fuel where it is cheaper. A more efficient vehicle helps most over time.

Not directly. This tool uses fuel economy and a price per gallon or litre. Electric running costs are based on kilowatt-hours and a price per unit of electricity instead.

No. The calculation runs in your browser, and nothing you enter is sent anywhere unless you Save a result, which stays on this device only.

• Fuel economy in automobiles (Wikipedia).
• Fuel efficiency (Wikipedia).
• Conversion of units (Wikipedia).