Fuel Calculator

Q: Should I use city, highway, or combined MPG?

Use the number that matches your drive. Combined — best for mixed driving and most trips. Highway — best for long road trips. City — best for stop-and-go traffic. Highway MPG gives a lower cost. City MPG gives a higher one.

Q: How do I split the fuel cost with friends?

Get your total cost from the Trip Cost tab, then divide it by the number of people riding. For example, a $86 trip split by 4 people is about $21.50 each.

Fuel Calculator

Updated Aug 7, 2026 By Jehan Wadia

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. If you only want one of those answers, the Gas Mileage Calculator, the Fuel Cost Calculator, and the Fuel Consumption Calculator each focus on a single job.

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, and the Electricity Cost Calculator can help you pin down your home charging rate.

Currency: Pick the money symbol you want, like USD, EUR, or GBP. For cross-border trips, the Currency Calculator converts your fuel spend back to your home money.

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. To see how driving fits into your whole footprint, try the Carbon Footprint Calculator.

Trip Cost tab: Enter your one-way distance and your car's fuel efficiency to get the total cost of the drive. Not sure how far it is? The Driving Distance Calculator and the Drive Time Calculator fill in that part.

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. Drivers who claim mileage at work can pair this with the Mileage Reimbursement Calculator.

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. The Break Even Calculator works the same idea for other purchases.

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: a US gallon is smaller than a UK (imperial) gallon. That is why the same car shows about 20% more MPG in UK numbers. Both are correct, they just use different gallons. Our Mileage Calculator handles the same conversions if you track fill-ups over many tanks.

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. If you charge from your roof, the Solar Panel Calculator shows how much of that power you could make yourself.

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, and check the clock on a long haul with the Speed Distance Time Calculator.

CO₂ From Driving

Burning fuel makes carbon dioxide. Each gallon of gasoline makes about 8.89 kg of CO₂, and each gallon of diesel makes about 10.16 kg. For EVs, the CO₂ depends on your power grid, and the US average is near 0.386 kg per kWh. Cleaner grids make that number smaller. The Carbon Equivalent Calculator and the Ecological Footprint Calculator put those totals in context.

Ways to Spend Less on Fuel

Slow down. Fuel use climbs fast above about 55–60 mph (90–100 km/h).
Keep tires at the right pressure. Soft tires drag and waste fuel — see the Tire Size Calculator and the Bike Tire Pressure Calculator for sizing and pressure basics.
Drop extra weight and remove roof racks when you are not using them.
Ease off hard starts and hard stops. Smooth driving can save up to 20% in city traffic.
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 — the Trade In Value Calculator and the Car Affordability Calculator cover the money side of that swap.

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 Auto Loan Calculator, the Car Lease Calculator, and the Car Depreciation Calculator so fuel savings are not wiped out by other costs.

Formulas used

Convert fuel economy to consumption (L/100 km)

c = \frac{235.2146}{E_{\text{MPG(US)}}} = \frac{282.4809}{E_{\text{MPG(Imp)}}} = \frac{100}{E_{\text{km/L}}}

Fuel (or energy) required for a trip

F = \frac{D_{\text{km}}}{100} \times c

Effective trip distance (round trip option)

D = d \times \left(\text{round trip} \;?\; 2 : 1\right),\qquad D_{\text{km}} = D \times \frac{L_u}{1000}

Total fuel / charging cost

C = F \times p,\qquad p = \frac{p_{\text{entered}}}{V_u}

Fuel efficiency from distance and fuel used

c = \frac{F}{D_{\text{km}}} \times 100,\qquad E_{\text{MPG(US)}} = \frac{235.2146}{c}

CO2 emissions

m_{CO_2} = F \times f_{CO_2}

Annual cost from periodic distance

C_{\text{year}} = \frac{D_{\text{period}} \times n}{100} \times c \times p,\quad n = 52,\,12,\,1

Break-even time for extra upfront cost

t = \frac{\Delta_{\text{upfront}}}{C_A - C_B}

Frequently asked questions

Should I use city, highway, or combined MPG?

Use the number that matches your drive.

Combined — best for mixed driving and most trips.
Highway — best for long road trips.
City — best for stop-and-go traffic.

Highway MPG gives a lower cost. City MPG gives a higher one.

Why is my real MPG lower than the number on the window sticker?

Sticker ratings come from lab tests. Real driving is harder on fuel. Speed, hills, cold air, A/C, roof racks, heavy loads, and fast starts all raise fuel use.

Use the Fuel Efficiency tab with your own fill-up numbers to get your true MPG.

How do I find my car's real MPG?

Do this at the pump:

Fill the tank all the way and reset your trip meter.
Drive normally until the tank is low.
Fill up again and write down the fuel added.
Put your trip miles and the fuel added into the Fuel Efficiency tab.

Two or three tanks in a row gives an even better average.

Does this calculator include tolls, food, or hotels?

No. It only counts fuel or charging cost. Parking, tolls, meals, and rooms are extra. Add those on your own for a full trip budget.

Can I compare a gas car and an electric car in the 3-vehicle table?

Not at the same time. All three vehicles use the same fuel type and same price.

To compare them, run the gas cars first and write down the cost. Then switch Fuel Type to Electric, enter your kWh price, and run the EV. Compare the two totals.

Can I use this for a truck, RV, motorcycle, or van?

Yes. Any vehicle works as long as you know its fuel efficiency. Just enter the MPG or L/100 km for that vehicle. Big rigs and RVs often sit near 6–12 MPG, so type the real number, not a car number.

How do I split the fuel cost with friends?

Get your total cost from the Trip Cost tab, then divide it by the number of people riding. For example, a $86 trip split by 4 people is about $21.50 each.

Why does my break-even result say Never?

That means Car B uses more fuel than Car A, so it never saves you money. You would pay more up front and more at the pump.

Check that you entered the units right. In L/100 km a lower number is better, but in MPG a higher number is better.

Why did my numbers change when I switched to Metric?

Nothing broke. The tool converts every value you typed. Miles become kilometers, gallons become liters, and MPG becomes L/100 km. The answer stays the same, just in new units.

Does towing a trailer change my fuel cost?

Yes, a lot. Towing can cut fuel economy by 20% to 50%. Enter your towing MPG, not your normal MPG. If you do not know it, try dropping your normal MPG by about a third for a rough guess.

How does cold weather change the results?

Cold air hurts fuel economy. Gas cars can lose about 10–20% in winter. EVs can lose 20–40% of range because heating the cabin and battery uses power.

For winter trips, lower your efficiency number so the cost is not too low.

Can I change the CO₂ number for my area?

Yes. The CO₂ box is editable. Gas and diesel numbers are close to fixed by chemistry, but electricity is not. If your power comes from wind, hydro, or solar, type a smaller kg per kWh. Coal-heavy grids need a bigger one.

How do I know if I can reach the next gas station on one tank?

Use the Fuel Needed tab. Enter the distance to the station and your MPG. If the fuel needed is more than what is in your tank, stop sooner.

Leave a safety cushion. Do not plan to arrive on empty.

Why is my cost per mile shown with four decimals?

Because it is a small number. A trip might cost only $0.1078 per mile. Cutting it to two decimals would hide real differences between cars. Multiply by 100 to see the cost per 100 miles.

Does the price of premium gas change the math?

Only through the price box. Type what you actually pay. Premium fuel does not raise MPG in a car built for regular gas, so your cost goes up with no gain.

What is a good MPG number today?

Small cars: 30–40 MPG (6–8 L/100 km)
Hybrids: 45–58 MPG (4–5 L/100 km)
SUVs: 22–28 MPG (8–11 L/100 km)
Pickups: 15–22 MPG (11–16 L/100 km)
EVs: 25–35 kWh per 100 miles

Do my numbers get saved?

No. Nothing is stored or sent anywhere. If you close or reload the page, the tool goes back to its default values. Write down or screenshot any result you want to keep.

Why do the results change while I am still typing?

The tool updates live with every keystroke. You do not have to press Calculate. That button just refreshes the answer if you want it. Reset puts everything back to the start.

Fuel prices keep moving. How should I plan for that?

Run the trip twice. Once at today's price, and once at a price about 20% higher. That gives you a low and high budget so a price jump does not surprise you on a long trip.

Is a hybrid entered the same way as a gas car?

Yes. Pick Hybrid and enter its combined MPG or L/100 km, plus the gas price. The math is the same as gasoline. Only plug-in hybrids that run mostly on battery need a separate electric run.

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