Fuel Consumption Calculator

Q: Can I use this calculator for diesel cars?

Yes. Select Diesel from the Fuel Type dropdown at the top. The calculator will use the correct CO₂ factor for diesel (2.68 kg per litre) in all results.

Q: How does the vehicle comparison work?

Click Add Vehicle to Compare . Name both vehicles and enter a different consumption rate for Vehicle B. The calculator runs the same trip with both rates and shows you which vehicle uses less fuel, costs less, or goes farther. A percentage difference tells you exactly how much one vehicle beats the other.

Updated Jul 23, 2026 By Jehan Wadia

Introduction

This free fuel consumption calculator helps you figure out how much fuel your car uses and what it costs. Enter your distance and fuel details to get results in L/100km, MPG, or km/L — all in seconds. You can switch between metric and imperial units with one click.

The calculator has four modes. Consumption Rate tells you how efficient your car is based on distance driven and fuel used. Trip Fuel Cost shows the total price of fuel for any trip. Trip Range estimates how far you can drive on the fuel left in your tank. Fuel Needed calculates how much fuel to buy and how many fill-ups a long trip will take.

You can also compare two vehicles side by side to see which one saves more fuel and money on the same trip. Every result includes a step-by-step breakdown of the math, a CO₂ emissions estimate, and a chart so you can see the numbers clearly. Whether you are planning a road trip or just want to track your car's fuel efficiency, this tool gives you the answers fast.

How to Use Our Fuel Consumption Calculator

Enter your trip details, fuel usage, and fuel price to calculate your car's fuel consumption rate, trip cost, driving range, or fuel needed. The calculator gives you results in multiple units, CO₂ emissions, and a step-by-step breakdown of the math.

General Settings

Unit System: Pick Metric (km and litres), Imperial US (miles and US gallons), or Imperial UK (miles and UK gallons). All your numbers will convert automatically when you switch.

Fuel Type: Choose Petrol, Diesel, or Hybrid. This sets the CO₂ emission factor used in your results.

Consumption Rate Mode

Distance Traveled: Type the total distance your car drove on the trip. If you need help figuring out the exact distance, try our driving distance calculator.

Fuel Used: Type the amount of fuel your car burned over that distance.

Trip Fuel Cost Mode

Distance: Type how far you plan to drive.

Fuel Consumption Rate: Enter your car's fuel consumption rate. Use the dropdown next to it to pick the unit, such as L/100km, km/L, MPG (US), or MPG (UK). If you need to calculate your rate first, use our gas mileage calculator.

Fuel Price: Enter the price you pay for one unit of fuel. Use the currency dropdown on the left to pick your currency symbol.

Trip Range Mode

Tank Capacity: Enter the full size of your car's fuel tank.

Current Fuel Level: Type how much fuel is in your tank right now, or drag the slider to set it as a percentage of your tank.

Fuel Consumption Rate: Enter your car's consumption rate and pick the unit from the dropdown.

Fuel Needed Mode

Trip Distance: Type the total distance of the trip you want to take.

Fuel Consumption Rate: Enter your car's consumption rate and choose the unit from the dropdown.

Fuel Price: Enter the cost per unit of fuel and select your currency.

Tank Capacity (optional): Enter your tank size if you want to see how many fill-ups the trip will need. Leave it blank to skip this.

Compare Vehicles

Add Vehicle to Compare: Click this button to open the comparison panel. Give each vehicle a name and enter a separate consumption rate for Vehicle B. The calculator will show which car is more efficient on the same trip. If you are comparing vehicles you are thinking about buying, our car affordability calculator can help you work out the purchase side of the equation.

Annual Fuel Cost Estimate

Trips per Week: Enter how many times you make this trip each week.

Weeks per Year: Enter how many weeks per year you drive this trip. The calculator multiplies your single trip cost to estimate your yearly fuel spending. You can use this figure alongside a budget calculator to plan your overall expenses.

What Is Fuel Consumption?

Fuel consumption is how much fuel your car uses to travel a certain distance. It tells you how efficient your vehicle is. A car that uses less fuel to go the same distance is more efficient, which saves you money and is better for the environment. You can explore your broader environmental impact with our ecological footprint calculator.

How Is Fuel Consumption Measured?

There are a few common ways to measure fuel consumption:

Litres per 100 kilometres (L/100km) — used in most countries. A lower number means better fuel economy.
Miles per gallon (MPG) — used in the United States and the United Kingdom. A higher number means better fuel economy. Note that a US gallon and a UK gallon are different sizes, so US MPG and UK MPG are not the same. Our gas mileage calculator can help you convert between these units.
Kilometres per litre (km/L) — another metric option. A higher number means your car goes farther on each litre of fuel.

What Affects How Much Fuel Your Car Uses?

Many things change how much fuel a car burns. Driving fast, carrying heavy loads, using the air conditioner, and having low tire pressure all make your car use more fuel. Stop-and-go city driving also uses more fuel than steady highway driving. Keeping your engine well maintained and your tires properly inflated helps your car run more efficiently. Your car's power-to-weight ratio and engine displacement also play a role in overall fuel economy.

What Is a Good Fuel Consumption Rate?

For most cars, a rate of 6 L/100km or less (about 39 MPG US or more) is considered excellent. A rate between 6 and 10 L/100km (about 24 to 39 MPG US) is average. Anything above 10 L/100km (below 24 MPG US) is considered poor. Small cars and hybrids tend to have the best rates, while trucks and SUVs tend to use more fuel. You can use our mileage calculator to track your car's real-world efficiency over time.

Fuel Consumption and CO₂ Emissions

When your car burns fuel, it releases carbon dioxide (CO₂) into the air. Petrol produces about 2.31 kg of CO₂ per litre, and diesel produces about 2.68 kg per litre. Knowing your fuel consumption helps you estimate how much CO₂ your driving adds to the atmosphere. Using less fuel means fewer emissions. To see the full picture of your carbon output — including driving, energy use, and more — try our carbon footprint calculator. If you are also looking to reduce overall vehicle costs, our gas cost calculator and car depreciation calculator can help you understand the true cost of owning and operating your car.

Formulas used

Fuel Consumption Rate

\text{L/100km} = \frac{F}{D} \times 100

Fuel Volume Needed for Trip

F = D \times \frac{r}{100}

Trip Fuel Cost

C = F \times p

Distance to Empty (Range)

R = \frac{V_{\text{cur}} \times 100}{r}

CO₂ Emissions

\text{CO}_2 = F \times e_f

Fill-Ups Required

N = \left\lceil \frac{F}{V_{\text{tank}}} \right\rceil

Frequently asked questions

How do I find out how much fuel my car used on a trip?

Fill up your tank completely. Write down the odometer reading. Drive normally until you need fuel again. Fill up the tank again and note how many litres or gallons it took. Write down the new odometer reading. Subtract the first reading from the second to get your distance. Then enter the distance and fuel amount into the Consumption Rate tab of this calculator to see your rate in L/100km, MPG, or km/L.

What is the difference between US MPG and UK MPG?

A US gallon is 3.785 litres and a UK gallon is 4.546 litres. Because a UK gallon is bigger, UK MPG numbers are always higher than US MPG for the same car. A car that gets 30 MPG (US) gets about 36 MPG (UK). This calculator converts between both automatically.

How do I convert L/100km to MPG?

Divide 235.215 by your L/100km number to get US MPG. Divide 282.481 by your L/100km number to get UK MPG. For example, 8 L/100km equals about 29.4 MPG (US) or 35.3 MPG (UK). This calculator does the conversion for you in every mode.

Why does the calculator show a CO₂ number?

Every litre of fuel your car burns releases CO₂ into the air. The calculator multiplies the fuel used by a standard emission factor — 2.31 kg per litre for petrol, 2.68 kg for diesel, and 1.16 kg for hybrid blended use. This helps you see the environmental impact of your driving.

What does the 10% reserve mean in Trip Range mode?

The calculator keeps 10% of your tank as a safety buffer. The refuel point tells you how far you can drive before your fuel drops to that 10% level. This gives you a warning distance so you do not run out of fuel completely.

Can I use this calculator for diesel cars?

Yes. Select Diesel from the Fuel Type dropdown at the top. The calculator will use the correct CO₂ factor for diesel (2.68 kg per litre) in all results.

How does the vehicle comparison work?

Click Add Vehicle to Compare. Name both vehicles and enter a different consumption rate for Vehicle B. The calculator runs the same trip with both rates and shows you which vehicle uses less fuel, costs less, or goes farther. A percentage difference tells you exactly how much one vehicle beats the other.

What should I enter for fuel price?

Enter the price you pay for one litre or one gallon of fuel at your local station. Use the currency dropdown to pick your currency symbol. The calculator uses this price to figure out your total trip cost and cost per kilometre or mile.

How accurate is this calculator?

The math is precise based on the numbers you enter. Real-world fuel use can vary because of traffic, weather, driving style, road conditions, and vehicle load. For the best accuracy, use fuel consumption data from your own fill-up records rather than the manufacturer's rated number.

What happens when I switch from metric to imperial units?

All your input values convert automatically. Distances change between kilometres and miles, volumes change between litres and gallons, and fuel prices adjust to match the new volume unit. You do not need to re-enter anything.

How do I estimate my yearly fuel cost?

Use the Trip Fuel Cost or Fuel Needed mode first. After you get a result, click Estimate Annual Fuel Cost. Enter how many trips you make per week and how many weeks per year you drive. The calculator multiplies your single trip cost by those numbers to give you an annual total.

Why is my fuel consumption worse than the manufacturer says?

Manufacturer ratings come from controlled lab tests. Real driving includes traffic, hills, wind, air conditioning, extra passengers, and cargo. City driving with frequent stops also uses much more fuel than steady highway speeds. Most drivers see fuel use 10% to 30% higher than the official rating.

How many fill-ups will I need for a long road trip?

Use the Fuel Needed mode. Enter your trip distance, consumption rate, fuel price, and your tank capacity. The calculator divides the total fuel needed by your tank size and rounds up to give you the number of fill-ups required.

Does the hybrid fuel type option work for plug-in hybrids?

The hybrid option uses a blended CO₂ factor of 1.16 kg per litre, which assumes a mix of electric and fuel driving. For plug-in hybrids, your actual emissions depend on how much you drive on battery versus fuel. Use this setting as a rough estimate, not an exact figure.

Can I use this calculator for motorcycles or trucks?

Yes. The math works for any vehicle that burns petrol or diesel. Enter the correct fuel consumption rate for your motorcycle, truck, or van, and the calculator will give you accurate results for fuel use, cost, range, and CO₂ emissions.

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