MPG Calculator

The MPG Calculator measures a vehicle's fuel economy based on the distance driven and the total fuel consumed during that trip. It simultaneously calculates and returns equivalent efficiency ratings in US miles per gallon (MPG), UK miles per gallon, liters per 100 kilometers (L/100 km), and kilometers per liter (km/L).

Formula

For a distance and fuel amount entered in compatible units:

$\text{L/100 km}=\frac{\text{Fuel used}}{\text{Distance}}\times100$ $\text{US MPG}=\frac{235.21}{\text{L/100 km}}$ $\text{UK MPG}=\frac{282.48}{\text{L/100 km}}$ $\text{km/L}=\frac{\text{Distance}}{\text{Fuel used}}$

The calculator expects distance and fuel inputs in the units represented by the form. Both values must be positive.

Worked example

If a car travels 600 km and uses 48 litres:

1. Fuel economy: 48 / 600 x 100 = 8.00 L/100 km.
2. US MPG: 235.21 / 8 = 29.40 MPG.
3. km/L: 600 / 48 = 12.50 km/L.

Reading the result

Lower L/100 km means less fuel used per distance. Higher MPG and km/L mean better fuel economy. The label is a broad comparison band from the implementation, not an official vehicle rating.

Questions

Why are US and UK MPG different?

A US gallon is smaller than an Imperial (UK) gallon, so the same vehicle has different numerical MPG values in each system.

Should I use the dashboard or pump figures?

For a real-world estimate, use the distance on the odometer and litres or gallons added at the pump over a complete fill-to-fill interval.

Does this account for driving conditions?

No. It reports the efficiency implied by your entered trip. Speed, traffic, temperature, load, tyre pressure, and terrain can change the next tank's result.

Limitations

The calculator does not correct for odometer error, partial fills, fuel blending, or manufacturer test conditions. Keep distance and fuel units consistent before interpreting the conversion.