MPG Calculator

What Is an MPG Calculator?

This free MPG calculator measures your vehicle’s actual real-world fuel economy from fill-up data. It shows your result in L/100km (metric), MPG US, and MPG UK simultaneously — making this MPG calculator useful worldwide, regardless of which unit system you use. In short, this MPG calculator tells you whether your vehicle is performing efficiently compared to benchmarks, or whether a drop in fuel economy might indicate a maintenance issue.

Manufacturer MPG figures are measured in controlled lab conditions and are typically 10–20% more optimistic than real-world driving. This MPG calculator uses your actual fill-up data to give you the truth about your vehicle’s efficiency on your roads, in your driving conditions.

How to Use This MPG Calculator

1. Fill up your tank completely and reset your trip odometer to zero.
2. Drive normally until your next fill-up — highway, city, or mixed.
3. Fill up again completely and note the litres added and the distance driven on the trip odometer.
4. Enter both values into this MPG calculator — your L/100km, MPG US, and MPG UK appear instantly with an efficiency rating.

How Does This MPG Calculator Work?

For example, if you drove 420 km and used 36 litres: L/100km = 36 ÷ 420 × 100 = 8.57 L/100km. MPG US = 235.21 ÷ 8.57 = 27.4 MPG. This MPG calculator applies these conversions automatically.

What Is a Good Result in This MPG Calculator?

• Under 6 L/100km (47+ MPG US): Excellent — typical of hybrids and efficient small cars.
• 6–8 L/100km (29–39 MPG US): Good — typical of modern fuel-efficient passenger cars.
• 8–11 L/100km (21–29 MPG US): Average — typical of larger sedans and small SUVs.
• 11–14 L/100km (17–21 MPG US): Below average — typical of larger SUVs and older vehicles.
• Above 14 L/100km (under 17 MPG US): Poor for a standard passenger vehicle — consider servicing.

Is This MPG Calculator Accurate?

This MPG calculator is accurate based on the data you enter. Fill-up method accuracy depends on filling to the same point each time. According to the US EPA fuel economy guide, highway driving typically gives 20–30% better fuel economy than city stop-start driving. Track highway and city driving separately in this MPG calculator for the most useful benchmarks for each driving scenario.

MPG Calculator — Frequently Asked Questions