MPG Calculator

What is MPG?

Miles Per Gallon (MPG) measures how far a vehicle can travel per gallon of fuel. It is the most common fuel economy unit in the United States and the United Kingdom, while most other countries use liters per 100 kilometers (L/100km). A critical difference: 1 UK gallon = 1.20095 US gallons. That means the same car will show a higher MPG figure in the UK than in the US, even though its real-world efficiency is identical.

Understanding all three units is useful when comparing cars across markets or reading international reviews. This calculator converts between MPG (US), MPG (UK), and L/100km so you can evaluate fuel economy no matter which unit is quoted.

How to Use

• When you fill your tank, reset the trip odometer or note the current mileage.
• Drive normally until the tank is low, then refuel and fill it all the way up.
• Record the distance driven and the amount of fuel used to refill.
• Pick the matching unit toggle, then enter distance and fuel used.
• Your fuel economy will display in all three units instantly.

Example

A Ford F-150 driver fills up, drives 300 miles, and refills with 15 gallons of gas. MPG = 300 / 15 = 20 MPG (US), which equals about 24 MPG (UK) or 11.8 L/100km. A Toyota Prius driver covering the same 300 miles might use only 6 gallons — that's 50 MPG, or roughly 4.7 L/100km.

MPG vs L/100km

The two units measure opposite things. Higher MPG = better (more distance per gallon). Lower L/100km = better (less fuel per 100 km). A quick conversion: L/100km = 235.215 / MPG(US). So 25 MPG ≈ 9.4 L/100km, and 50 MPG ≈ 4.7 L/100km. When comparing specs, always check which unit is being used.

Improving Your Gas Mileage

• Keep tires properly inflated. Underinflated tires can drop fuel economy by 3% or more.
• Use cruise control on highways to maintain a steady speed and reduce fuel waste from acceleration.
• Lighten the load. Remove roof racks and unnecessary cargo — extra weight and drag cut efficiency.
• Accelerate smoothly and avoid hard braking. Aggressive driving can reduce mileage by 15–30% on the highway.

Frequently Asked Questions

What's a good MPG for a car? For a modern sedan, 30+ MPG (US) is solid. Hybrids reach 45–55 MPG, while SUVs and trucks typically sit at 18–25 MPG.

Why does the UK gallon differ from the US gallon? The UK (imperial) gallon is defined as 4.54609 liters, while the US gallon is 3.78541 liters. 1 UK gallon = 1.20095 US gallons, so UK MPG figures look about 20% higher for the same vehicle.

How do I calculate MPG accurately? Fill up completely, reset the trip meter, drive until low, and fill up again. Divide miles driven by gallons added at the second fill-up. Repeat over several tanks for a reliable average.

Is my data stored? No. All calculations run entirely in your browser. No driving data is collected or transmitted.

Formula

MPG (US) = miles / US gallons. MPG (UK) = miles / UK gallons. L/100km = 235.215 / MPG(US), or (liters × 100) / kilometers.