Gas Mileage Calculator
Calculate your vehicle gas mileage in MPG US, MPG UK, km/L, and L/100km. Enter distance and fuel used for instant fuel economy results with comparison charts.
About This Calculator
The Gas Mileage Calculator helps you measure your vehicle fuel efficiency in all major units used worldwide. Enter the distance you have traveled and the fuel you have used, and instantly see your gas mileage in miles per US gallon (MPG), miles per UK gallon (MPG UK), kilometers per liter (km/L), and liters per 100 kilometers (L/100km). Whether you are tracking your daily commute, planning a road trip, or evaluating a potential vehicle purchase, this calculator provides a complete picture of fuel economy across every measurement system.
How Gas Mileage Is Calculated
The calculator converts all inputs to a consistent base unit before computing each metric. If you enter distance in miles and fuel in gallons, MPG US is simply distance divided by fuel. For MPG UK, the same miles are divided by fuel gallons converted to imperial gallons (multiplied by 0.832674). For metric results, miles are converted to kilometers and gallons to liters using standard conversion factors: 1 mile = 1.60934 kilometers, 1 US gallon = 3.78541 liters.
L/100km is the inverse of km/L multiplied by 100 — a lower value means better fuel economy. This is the standard unit in Europe, Canada, Australia, and most of the world. MPG (both US and UK) uses a larger-number-is-better scale, which can cause confusion when comparing across systems.
Regional Notes
United States: Gas mileage is universally expressed in miles per US gallon (MPG). The EPA provides official fuel economy ratings for all new vehicles. A typical sedan achieves 30-40 MPG on the highway. US gallons are the smallest gallon unit at 3.785 liters.
United Kingdom: Fuel economy is expressed in miles per imperial gallon (MPG UK) on older vehicles and in many publications, though new car specs increasingly use L/100km. The UK imperial gallon is 4.546 liters, about 20% larger than a US gallon, so the same car shows a higher MPG UK rating.
India and other metric countries: Fuel efficiency is typically given in km/L or L/100km. Indian car manufacturers quote both units, and the government fuel efficiency standards use km/L. In Europe and Asia, L/100km is the dominant standard for vehicle specifications and regulation.
Frequently Asked Questions
How do you calculate gas mileage?
Gas mileage is calculated by dividing the distance traveled by the fuel used. In US units, that is miles driven divided by gallons of fuel used to get MPG. In metric units, it is kilometers traveled divided by liters of fuel used to get km/L. To get L/100km, divide liters of fuel by kilometers traveled and multiply by 100.
What is the difference between MPG US and MPG UK?
US and UK gallons are different sizes. A US gallon equals 3.785 liters while a UK imperial gallon equals 4.546 liters, making a UK gallon about 20% larger. This means the same vehicle will show a higher MPG value in UK gallons. To convert, multiply US MPG by 1.201 to get UK MPG.
What is a good gas mileage for a car?
A good gas mileage depends on the vehicle. For US MPG, over 40 MPG is excellent, 30-40 MPG is good, and under 25 MPG is below average. In L/100km, under 6 L/100km is excellent, 6-8 L/100km is good, and over 10 L/100km is poor. Modern hybrids can achieve over 50 MPG.
How can I improve my car fuel economy?
Drive at steady speeds around 55-65 mph (90-105 km/h), maintain proper tire pressure, remove excess weight, avoid aggressive acceleration and braking, use cruise control on highways, reduce idling time, keep your vehicle properly maintained with regular oil changes and air filter replacements, and use the recommended grade of motor oil.
How do I manually calculate my car MPG?
Fill your tank completely, reset the trip odometer to zero, drive normally for at least 100 miles, then fill the tank again and note the gallons pumped. Divide the miles driven by the gallons used. For example, 300 miles divided by 10 gallons equals 30 MPG. For L/100km, divide liters used by kilometers driven and multiply by 100.
Is gas mileage the same as fuel economy?
Gas mileage and fuel economy refer to the same concept of how efficiently a vehicle uses fuel. Gas mileage is commonly expressed in miles per gallon (MPG) in the US and UK, while fuel economy can be expressed in km/L, L/100km, or MPG. Both terms measure the relationship between distance traveled and fuel consumed.
Why do different countries use different gas mileage units?
The US uses MPG with US gallons as part of its customary measurement system. The UK historically used MPG with imperial gallons but increasingly uses L/100km. Most other countries including Europe, Canada, Australia, and Japan use L/100km as the standard metric unit. km/L is used in some markets like India and Japan. This calculator supports all four major units.