Fuel Cost Calculator
- Updated
- Imperial and metric
- Free, no sign-up
Results
Fuel for 250 mi: 8.33 US gal costing $29.17.
| mpg (US) | Fuel | Cost |
|---|---|---|
| 15 | 16.67 US gal | $58.33 |
| 20 | 12.5 US gal | $43.75 |
| 25 | 10 US gal | $35.00 |
| 30 | 8.33 US gal | $29.17 |
| 35 | 7.14 US gal | $25.00 |
| 40 | 6.25 US gal | $21.88 |
| 50 | 5 US gal | $17.50 |
Price per US gallon. Real-world economy varies with speed, traffic, loads, air conditioning and weather, so treat the result as an estimate.
How to use the fuel cost calculator
- Choose US / Imperial for miles or Metric for kilometers, and enter the one-way distance. Pick Round trip to double it.
- Enter your car's fuel economy and its unit. UK drivers can keep miles and choose mpg (UK gallons).
- Enter the fuel price and whether it is per US gallon, UK gallon or liter, plus the number of people sharing the cost.
- Read the cost, the fuel needed and the cost per mile or km. The table shows the same trip in a more or less efficient car.
Fuel cost formula
Cost = fuel × price per unit · Cost per person = cost ÷ people
L/100 km = 235.215 ÷ mpg (US) = 282.481 ÷ mpg (UK) = 100 ÷ km/L
The calculator converts everything to liters and kilometers, works out the fuel used, then converts it to the unit the price is quoted in. The constants come from the exact definitions: a mile is 1.609344 km, a US gallon 3.785411784 liters and a UK (imperial) gallon 4.54609 liters. That is why the same car shows a higher mpg figure in the UK than in the US: the UK gallon is about 20% larger.
Worked examples
A 250-mile drive there and back is 500 miles. At 30 mpg the car uses 500 ÷ 30 = 16.67 US gallons, and at $3.50 a gallon the fuel costs $58.33, about 11.7 cents a mile. Shared by four people, that is $14.58 each.
In metric, a 400 km trip in a car that uses 7 L/100 km needs 400 × 7 ÷ 100 = 28 liters. At €1.80 per liter the fuel costs €50.40, or 12.6 cents per km.
Fuel cost per 100 miles
| Fuel economy | $3.00/gal | $3.50/gal | $4.00/gal | $4.50/gal | $5.00/gal |
|---|---|---|---|---|---|
| 20 mpg (US) | $15.00 | $17.50 | $20.00 | $22.50 | $25.00 |
| 25 mpg (US) | $12.00 | $14.00 | $16.00 | $18.00 | $20.00 |
| 30 mpg (US) | $10.00 | $11.67 | $13.33 | $15.00 | $16.67 |
| 35 mpg (US) | $8.57 | $10.00 | $11.43 | $12.86 | $14.29 |
| 40 mpg (US) | $7.50 | $8.75 | $10.00 | $11.25 | $12.50 |
| 50 mpg (US) | $6.00 | $7.00 | $8.00 | $9.00 | $10.00 |
Fuel cost per 100 km
| Fuel economy | €1.50/L | €1.70/L | €1.90/L | €2.10/L |
|---|---|---|---|---|
| 4 L/100 km | €6.00 | €6.80 | €7.60 | €8.40 |
| 5 L/100 km | €7.50 | €8.50 | €9.50 | €10.50 |
| 6 L/100 km | €9.00 | €10.20 | €11.40 | €12.60 |
| 7 L/100 km | €10.50 | €11.90 | €13.30 | €14.70 |
| 8 L/100 km | €12.00 | €13.60 | €15.20 | €16.80 |
| 10 L/100 km | €15.00 | €17.00 | €19.00 | €21.00 |
The prices in these tables are examples only, not current pump prices. Enter your own in the calculator.
Fuel economy unit conversions
| mpg (US) | mpg (UK) | L/100 km | km/L |
|---|---|---|---|
| 20 | 24 | 11.76 | 8.5 |
| 25 | 30 | 9.41 | 10.6 |
| 30 | 36 | 7.84 | 12.8 |
| 35 | 42 | 6.72 | 14.9 |
| 40 | 48 | 5.88 | 17 |
| 50 | 60 | 4.7 | 21.3 |
Sharing fuel costs
For a car pool or road trip, decide first what you are sharing. Splitting only the fuel is simplest: divide the cost by everyone in the car, including the driver, which is what the passengers field does. Some groups also add an amount per mile for wear on the driver's car. Official per-mile rates, which cover fuel, maintenance and depreciation, are much higher than fuel alone, so agree on the approach before you set off.
Tips for a better estimate
- Use real-world economy. Official ratings come from standard test cycles. Your own average from a few fill-ups, which the gas mileage calculator works out, is usually closer for your driving.
- Highway speeds matter. Air resistance rises steeply with speed, so a fast highway trip can use noticeably more fuel than the same distance at moderate speed.
- Check the gallon. mpg figures from UK sources use imperial gallons; US figures use US gallons. Mixing them makes a trip look about 17% cheaper or 20% more expensive than it is.
- Fuel isn't the whole cost of driving. For business trips, reimbursement rates cover wear, insurance and depreciation too; see the mileage reimbursement calculator.
Frequently asked questions
How do I calculate the fuel cost of a trip?
Divide the distance by your fuel economy to get the fuel needed, then multiply by the price. A 500-mile round trip at 30 mpg uses 16.67 US gallons, which costs $58.33 at $3.50 a gallon, or $14.58 each for four people.
How do I calculate fuel cost with L/100 km?
Multiply the distance in km by the L/100 km figure and divide by 100 to get liters, then multiply by the price per liter. A 400 km trip at 7 L/100 km needs 28 liters, which costs €50.40 at €1.80 a liter.
What is the difference between US and UK mpg?
The gallon. A US gallon is 3.785 liters and a UK (imperial) gallon is 4.546 liters, so the same car shows a higher mpg figure in the UK. 30 mpg in US gallons is about 36 mpg in UK gallons, or 7.84 L/100 km.
How do I convert mpg to L/100 km?
Divide 235.215 by the US mpg figure, or 282.481 by the UK mpg figure. 30 mpg (US) is 7.84 L/100 km and 50 mpg (UK) is 5.65 L/100 km. The conversion works both ways: 235.215 ÷ 7.84 gives back 30 mpg.
What is the fuel cost per mile?
Divide the fuel price by the mpg. At $3.50 a gallon and 30 mpg, fuel costs about 11.7 cents a mile; at 25 mpg it is 14 cents. That is fuel only, not the full cost of running a car.