Fuel Consumption Calculation Formula

The most accurate way to calculate fuel consumption is by using the formula: (Litres used ÷ Distance travelled) × 100. This gives you litres per 100 kilometres (L/100km), the standard metric measurement. For example, if you use 5 litres of fuel to travel 100 miles, first convert miles to kilometres (100 miles ≈ 160.9 km), then apply the formula: (5 ÷ 160.9) × 100 ≈ 3.11 L/100km.

For those preferring miles per gallon (MPG), the formula is: (Distance in miles ÷ Litres used) × 4.546. The 4.546 factor converts litres to gallons. If your car covers 300 miles on 40 litres, the MPG is (300 ÷ 40) × 4.546 ≈ 34.1 MPG.

Key tips for accurate measurement:

1. Fill your tank completely and reset the trip meter.
2. Drive as you normally would until the next refill.
3. Note the litres added and distance travelled since the last fill-up.
4. Apply the formula based on your preferred unit (L/100km or MPG).

Modern cars with onboard computers often display real-time consumption, but manual calculations help verify accuracy. Factors like driving style, traffic, and load affect results, so averaging multiple fill-ups gives a clearer picture.

A mechanic’s perspective: Fuel consumption isn’t just about the formula—it’s about how your car behaves. If your MPG drops suddenly, check for issues like underinflated tyres, clogged air filters, or faulty oxygen sensors. Even small maintenance oversights can skew calculations. For example, a dirty air filter can increase consumption by up to 10%. Always cross-reference manual calculations with your car’s diagnostics for discrepancies.

Car fuel consumption calculator formula: Fuel consumption per 100 kilometres = Fuel used ÷ Distance travelled × 100.

Car fuel consumption calculator formula:

Fuel consumption per 100 kilometres = Fuel used ÷ Distance travelled × 100.

1. Start by recording every fuel refill from the beginning of vehicle usage, then divide the total fuel consumed by the total mileage. Using the above formula will allow you to calculate your car's fuel consumption per 100 kilometres with reasonable accuracy.
2. Divide the amount of fuel you've just refuelled (in litres) by the kilometres (km) shown on your trip odometer, then multiply by 100 to obtain a fairly accurate figure for your vehicle's fuel consumption per 100 kilometres.
3. Fuel cost ÷ Petrol price = Total fuel volume, Total fuel consumption ÷ 10 = The vehicle's fuel consumption per 100 kilometres.

Additional information: What does fuel consumption signify? Some people refer to 'how many litres' when discussing fuel consumption per 100 kilometres. A car's fuel consumption isn't solely determined by the vehicle itself, but is also inextricably linked to the driver's habits and road conditions. Poor driving habits combined with frequent travel on congested roads will inevitably result in higher fuel consumption. When driving, to improve fuel efficiency, one should avoid sudden acceleration and harsh braking, maintaining a steady speed whenever possible - this is the most fuel-efficient way to drive. Unnecessary overtaking should also be avoided. Regular driving on congested routes will significantly increase a vehicle's fuel consumption. In traffic jams, cars often have to stop and start repeatedly. During acceleration, the engine requires considerable power output. If the vehicle is constantly stopping and starting, fuel consumption will undoubtedly rise. Moreover, when driving in congested conditions, the car's engine spends considerable time idling. While idling, the vehicle's mileage doesn't increase, yet the engine continues to consume fuel, which also contributes to higher fuel consumption per 100 kilometres.