Fill the tank, then enter the distance since the last full tank and how much fuel went in.
This gas cost calculator works out how much fuel a trip needs and what it costs from the distance, your car’s fuel economy and the price of gas. It accepts miles or kilometers and mpg, L/100 km or km/L, doubles the distance for a round trip and splits the total between passengers.
How to use
- Fuel cost: enter the distance (km or miles), your car’s consumption in L/100 km, km/L or mpg, and the fuel price per liter or gallon.
- Don’t know your consumption? Tap “From a fill-up” and enter the distance since the last full tank and the fuel you just added.
- Turn on Round trip to double the distance, and set People to split the cost.
- Electricity: enter your price per kWh, then list your appliances with their power in watts and hours of use per day. Pick a common appliance from the list or add your own.
- Totals per day, month and year appear at once, with each appliance’s share. Tap a result to copy it.
- Liters needed = distance × L/100 km ÷ 100. 1 US gallon = 3.785 L and 1 UK gallon = 4.546 L, so UK mpg figures are higher for the same car.
- Real-world consumption depends on speed, traffic, load and climate control; the official figure is usually optimistic.
- kWh = watts × hours ÷ 1,000. Fridges, freezers and heaters cycle on and off, so the preset uses an average power rather than the label maximum.
- Your price per kWh is on your electricity bill. Add standing charges and taxes separately if your bill has them.
- Your appliance list and units are saved in this browser.
The formula
Fuel needed = distance ÷ mpg, or distance × L/100 km ÷ 100. Cost = fuel needed × price. A 450-mile drive at 28 mpg needs about 16.1 gallons; at $3.40 a gallon that is $54.64.
To convert between units: L/100 km = 235.2 ÷ US mpg, or 282.5 ÷ UK mpg. 30 US mpg is 7.8 L/100 km. A US gallon is 3.785 liters and a UK gallon 4.546 liters, so the same car shows a higher mpg figure in the UK.
Getting a realistic number
Official economy figures are measured on a test cycle and are usually optimistic. Highway speeds above about 60 mph (100 km/h), heavy loads, roof boxes, cold weather and air conditioning all raise consumption. Use your car’s trip computer or a full-tank-to-full-tank measurement for the best estimate. Your units and last values are saved in this browser.
Frequently asked questions
How do I calculate gas cost for a trip?
Divide the distance by your mpg to get gallons, then multiply by the price per gallon. 300 miles at 25 mpg and $3.50 a gallon is 12 gallons, or $42.
How do I split gas money between friends?
Turn on Round trip if you are coming back, then set People. The total cost is divided equally between everyone in the car.
How do I convert mpg to L/100 km?
Divide 235.2 by US mpg. 25 mpg is 9.4 L/100 km and 40 mpg is 5.9 L/100 km. For UK mpg divide 282.5 instead.
Why is my real fuel use higher than the official figure?
Official tests use gentle driving. Speed, traffic, cold starts, cargo and climate control usually add 10–30% in daily use.
Does it include tolls or wear and tear?
No. It counts fuel only. Add tolls, parking or a per-mile allowance yourself if you need a full trip cost.