Fuel Economy Converter

• •Use the Fuel Economy Converter when you need accurate results quickly without the risk of manual computation errors or unit conversion mistakes.
• •Use it to verify calculations made by hand or in spreadsheets — an independent check can catch errors before they lead to costly decisions.
• •Use it to explore how changing input parameters affects the output — a quick way to develop intuition and identify the most influential variables.
• •Use it when collaborating with others to ensure everyone is working from the same numbers and applying the same assumptions.

The Fuel Economy Converter is a free, browser-based calculation tool for engineers, students, and technical professionals. Convert fuel economy between miles per gallon (US), miles per gallon (UK), liters per 100 kilometers, kilometers per liter, and miles per liter. Compare vehicle efficiency across measurement systems used in different countries around the world. It implements standard formulas and supports both metric (SI) and imperial unit systems with automatic unit conversion. All calculations are performed instantly in your browser with no data sent to a server. Use this calculator as a quick reference and sanity-check tool during design, analysis, and learning. Always verify results against primary engineering references and applicable standards for any safety-critical application.

The Fuel Economy Converter translates vehicle efficiency ratings between the measurement systems used around the world. The United States uses miles per US gallon (mpg). The United Kingdom uses miles per Imperial gallon. Most of Europe, Asia, and Australia use liters per 100 kilometers (L/100km), while Japan and some other countries prefer kilometers per liter (km/L). Because fuel economy is an inverse relationship (distance per volume vs. volume per distance), the conversion involves reciprocals rather than simple multiplication, which this tool handles automatically. It is essential for comparing vehicles across international markets.

• !Confusing US and UK gallons when comparing mpg ratings. A car rated 40 mpg (UK) is actually less efficient than it appears to an American, as it equals about 33.3 mpg (US).
• !Linearly interpolating mpg improvements. Going from 15 to 25 mpg saves much more fuel than going from 35 to 45 mpg, even though both are 10 mpg improvements.
• !Forgetting that L/100km is inversely related to mpg. A smaller L/100km number means better efficiency, while a larger mpg number means better efficiency.