Introduction
This fuel calculator tells you how much a drive will cost. Type in your distance, your car's gas mileage, and the price of fuel. You get the total cost right away.
You can use it three ways:
- Trip Cost: find out what a drive will cost you.
- Fuel Efficiency: find your real MPG or L/100 km from a tank of gas.
- Fuel Needed: find how many gallons or liters a trip will take.
It works for gas, diesel, hybrid, and electric cars. You can pick miles or kilometers, gallons or liters, and your own money type. The tool also shows your CO₂ emissions, your cost per mile, and what you spend in a year.
Want to compare cars? Put in up to three vehicles and see which one is cheapest for the same trip. You can also check how long it takes for a car with better gas mileage to pay back its higher price. Every answer comes with the math steps, so you can see how it works.
How to use our Fuel Calculator
Enter your trip distance, your car's fuel efficiency, and the price of fuel. The calculator shows your total fuel cost, how much fuel you need, cost per mile or km, CO₂ emissions, yearly costs, and a side-by-side vehicle comparison.
Unit System: Pick Imperial/US (miles, gallons) or Metric (km, liters). Every value you typed switches over for you.
Fuel Type: Choose gasoline, diesel, hybrid, or electric. Picking electric swaps the inputs to kWh.
Currency: Pick the money symbol you want, like USD, EUR, or GBP.
Fuel Price: Type what you pay for fuel, then pick per gallon, per liter, or per kWh.
CO₂ Emission Factor: Leave the default EPA number, or type your own to change the CO₂ math.
Show Fuel Volume In: Choose gallons, liters, or kWh for the fuel results.
Show CO₂ In: Choose pounds, kilograms, or metric tons for the emission results.
Trip Cost tab: Enter your one-way distance and your car's fuel efficiency to get the total cost of the drive.
Fuel Efficiency tab: Enter the distance you drove and the fuel you used to find your real MPG, L/100 km, or kWh use.
Fuel Needed tab: Enter the distance and fuel efficiency to see how much fuel or charge the trip takes.
Round trip switch: Turn this on to double the distance for the drive back home.
Show Main Result In: Pick the unit for your top efficiency answer, like MPG or L/100 km.
Compare Up To 3 Vehicles: Type a trip distance, then name each car and enter its efficiency. The cheapest car is marked green.
Annual Cost Estimate: Enter how far you drive and pick week, month, or year to see your fuel cost over time.
Break-Even Inputs: Enter two cars, their efficiency, your yearly distance, and how much more Car B costs. You will see the yearly savings and how long it takes to pay off.
Calculate and Reset: Results update as you type. Press Calculate to refresh, or Reset to start over.
Fuel Costs and Fuel Economy Explained
Every trip you drive burns fuel, and that fuel costs money. Three numbers control that cost: how far you drive, how much fuel your car uses per mile or kilometer, and the price of fuel where you fill up. Change any one of them and your trip cost changes too.
What Fuel Efficiency Means
Fuel efficiency (also called fuel economy) tells you how far your car goes on a set amount of fuel. Different countries write it in different ways:
- MPG (miles per gallon): used in the US and UK. A higher number is better.
- L/100 km (liters per 100 km): used in Canada and most of Europe. A lower number is better.
- km/L: common in Japan, India, and parts of Asia. Higher is better.
Watch out: the UK (Imperial) gallon is about 20% larger than the US gallon.7 That is why the same car shows about 20% more MPG in UK numbers. Both are correct, they just use different gallons.
Electric Cars Use kWh
An EV does not burn liquid fuel, so its "fuel" is measured in kilowatt-hours (kWh) of electricity. EV ratings show up as kWh/100 mi, kWh/100 km, mi/kWh, or MPGe. MPGe means "miles per gallon equivalent," which lets you compare an EV to a gas car using one energy rule: 33.7 kWh equals the energy in one gallon of gasoline.1
How Trip Cost Works
The math is simple. First find the fuel you need, then multiply by the price:
- Fuel needed = distance ÷ MPG (or distance × L/100 km ÷ 100)
- Trip cost = fuel needed × price per gallon or liter
- Round trips double the distance, so they double the fuel and the cost
Fuel is rarely the only road expense. Add highway fees with the Toll Calculator.
CO₂ From Driving
Burning fuel makes carbon dioxide. Burning a gallon of gasoline creates about 8,887 grams of CO₂, and a gallon of diesel about 10,180 grams.2 For EVs, the CO₂ depends on your power grid. In 2023, U.S. power plants emitted about 0.81 pounds of CO₂ for each kWh they generated.3 That is about 0.367 kg per kWh. Cleaner grids make that number smaller.
Ways to Spend Less on Fuel
- Slow down. Gas mileage usually decreases rapidly at speeds above 50 mph.4
- Keep tires at the right pressure. Soft tires drag and waste fuel.5
- Drop extra weight and remove roof racks when you are not using them.4
- Ease off hard starts and hard stops. Aggressive driving can lower gas mileage by roughly 10% to 40% in stop-and-go traffic.4
- Do not idle for long. An idling engine gets zero miles per gallon.
- Keep up with oil changes, air filters, and tune-ups.
Why Small MPG Gains Matter Most on Thirsty Cars
Going from 15 to 20 MPG saves more fuel than going from 40 to 50 MPG over the same miles. The reason is that low-MPG vehicles start out burning far more fuel, so each step up cuts a bigger amount. This is worth knowing when you compare a truck to a small car or plan a vehicle trade.
Annual and Break-Even Costs
Fuel is a repeat bill, not a one-time one. Drivers who cover about 12,000 miles (roughly 20,000 km) a year can spend thousands on fuel over time. If a more efficient car costs extra up front, divide that extra price by your yearly fuel savings. The answer is how many years it takes to earn the money back. Before you buy, run the numbers through the Car Depreciation Calculator so fuel savings are not wiped out by other costs.