Fuel Economy Converter
Convert between L/100km, km/L, mpg (US), mpg (UK), L/km, and L/mi. Type in any unit; all others update instantly.
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About This Converter
This fuel economy converter supports 6 common units and correctly handles the inverse relationship between consumption-based metrics (L/100 km, L/km, L/mi) and efficiency-based metrics (km/L, mpg). It uses exact gallon definitions -- 3.785411784 L for the US gallon and 4.54609 L for the UK imperial gallon -- so your results match official EPA and WLTP ratings. Whether you are comparing car specs across countries, planning a road trip budget, or shopping for a fuel-efficient vehicle, this tool gives you instant clarity.
Fuel-Saving Tips & FAQ
What everyday habits save the most fuel?
Drive smoothly: anticipate traffic, keep a steady speed, and avoid hard acceleration/braking. On highways, using cruise control helps maintain efficiency on flat roads.
What speed is most efficient?
Most cars are most efficient around 70–95 km/h (45–60 mph). Above that, aerodynamic drag rises quickly and economy drops.
How does tire pressure affect fuel economy?
Under-inflated tires increase rolling resistance. Check pressures monthly and set them to the door-jamb sticker (cold). Even a small drop can cost noticeable fuel.
Does extra weight or roof gear matter?
Yes. Remove unnecessary cargo. Roof boxes/racks add drag at speed; take them off when not in use.
Should I idle the engine to "warm up"?
No for modern cars. Idling wastes fuel; drive gently after start. Turn the engine off if stopped for more than ~60 seconds where safe/legal.
AC vs. windows: which uses less fuel?
At city speeds, open windows can be fine. At highway speeds, A/C may be better than open windows because of drag. Use A/C moderately and recirculate when possible.
How do short trips affect fuel use?
Cold engines are less efficient. Combine errands to reduce cold starts, and choose routes with fewer stops where possible.