MPG Calculator

What Is an MPG Calculator?

An MPG calculator determines a vehicle's fuel economy from the distance it travels and the amount of fuel it consumes. MPG stands for miles per gallon and is commonly used to compare vehicle fuel efficiency.

This calculator also converts fuel economy between UK MPG, US MPG and litres per 100 kilometres. This is useful when comparing vehicle specifications, fuel economy figures from different countries or real-world fuel consumption measurements.

Why Use the MPG Calculator?

Fuel economy can be expressed using different measurement systems. This calculator provides several equivalent figures from the same journey data, making it easier to understand and compare vehicle efficiency.

How to Use the MPG Calculator

Use a measured journey whenever possible for a more representative real-world fuel economy calculation.

1. Enter the distance travelled — Enter the total distance covered during the journey and select miles or kilometres.
2. Enter the fuel used — Enter the amount of fuel consumed and select litres, UK imperial gallons or US gallons.
3. Calculate the result — Select "Calculate MPG" to calculate the vehicle's fuel economy.
4. Compare the results — Review the equivalent UK MPG, US MPG, litres per 100 kilometres and litres per mile figures.

How Is MPG Calculated?

Miles per gallon is calculated by dividing the distance travelled in miles by the quantity of fuel consumed in gallons. The type of gallon matters because a UK imperial gallon and a US gallon contain different volumes of fuel.

When fuel usage is provided in litres, the calculator converts the litre measurement into the appropriate gallon measurement before calculating MPG. It also converts the result into litres per 100 kilometres, which is another widely used method of expressing fuel economy.

UK MPG vs US MPG

UK MPG and US MPG are not directly interchangeable because they use different gallon sizes. One UK imperial gallon is approximately 4.546 litres, while one US gallon is approximately 3.785 litres. Consequently, a vehicle's numerical UK MPG figure is higher than its equivalent US MPG figure.

MPG vs Litres per 100 km

MPG measures how far a vehicle can travel using a gallon of fuel, so a higher MPG indicates better efficiency. Litres per 100 km measures how much fuel is needed to travel 100 kilometres, so a lower L/100 km figure indicates better efficiency.

Understanding Real-World Fuel Economy

Official fuel economy figures are useful for comparing vehicles under standardised testing conditions, but real-world fuel economy can differ. Traffic, driving style, speed, acceleration, weather, road conditions, vehicle load, tyre pressure and air conditioning can all affect fuel consumption.

For a representative personal MPG calculation, record the distance travelled and fuel added over normal driving conditions. Repeating the measurement across several journeys can provide a more useful average than relying on a single trip.

Frequently Asked Questions