Fuel cost calculator
What will the drive cost in gas? Enter the distance, your car's fuel economy and the pump price. The answer updates as you type, in US, UK or metric units.
Split the cost, tolls & currency
Adjust the numbers to see your trip.
How the calculator works
Trip fuel cost is two steps: fuel needed = distance ÷ MPG, then cost = fuel needed × price. In litres-per-100-km countries the first step is distance × L/100km ÷ 100. For UK miles-per-gallon the tool converts imperial gallons (4.546 L) to litres, because UK pumps price by the litre.
Worked example: a 450-mile drive in a 32 mpg car uses 450 ÷ 32 = 14.1 gallons. At $3.60 a gallon that is 14.1 × 3.60 = $50.63 each way, or $101.25 round trip, which is about $25 each for four people.
What actually moves your trip cost
Your MPG is not a fixed number. Drag the speed and toggle the habits below to see how the same trip's fuel bill changes. The calculator above assumes typical ~65 mph highway driving.
Effective economy: 86% of what the car manages at 55 mph.
Why it works this way: air resistance rises with the square of speed, so past about 50–55 mph each extra 5 mph costs roughly 7% more fuel. FuelEconomy.gov puts aggressive driving at a 15–30% penalty on the highway and says a roof box can cut economy by up to 25% at interstate speeds. The figures here are mid-range values from that guidance, not measurements of your car. Understanding the numbers behind your habits is easier when you can play with them, which is what these hands-on explainers let you do.
Ask about this trip
An AI assistant reads the figures above and answers in plain English. It only runs when you press the button; the calculator works without it.
Getting a realistic number
- Use your real MPG. Window-sticker ratings are measured in lab cycles. Most drivers see a little less. Measure yours with the MPG calculator or keep a fuel log.
- Price for where you will fill up. Gas is usually dearer at motorway and interstate service areas than in towns a few minutes off the highway.
- Add distance for detours. Mapping apps give door-to-door distance; add 5–10% for fuel stops, food and wrong turns.
- Driving electric? Use the EV charging cost calculator. In the UK, the petrol cost calculator works in pence per litre.
Questions drivers ask
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 of fuel. For 300 miles in a 28 mpg car with gas at $3.75: 300 ÷ 28 = 10.7 gallons, and 10.7 × $3.75 = $40.18. Double it for a round trip.
What MPG should I use if I don't know mine?
Use the combined rating for your model on FuelEconomy.gov (US) or the manufacturer's figure, then knock off about 10–15% for real-world driving. Better still, measure it yourself with the MPG calculator on your next fill-up.
Does highway or city driving change the cost?
Yes. Most gasoline cars do best at a steady 45–55 mph; fuel use rises quickly above that because aerodynamic drag grows with the square of speed. Stop-and-go traffic also costs more than steady cruising. Hybrids are the exception: they often do better in town.
How do I split gas money fairly?
The simplest fair split is total fuel cost divided by everyone in the car, including the driver. Tick "include driver" off if the passengers are covering the driver's share as thanks for driving. Tolls and parking can be added on top.
Is fuel the whole cost of driving?
No. Fuel is usually a quarter to a third of what a car costs per mile once you add depreciation, insurance, maintenance and tyres. Use the cost-per-mile calculator for the full picture, or the IRS mileage rate as a benchmark.