Gas Mileage (MPG) Calculator

How it works

Miles per gallon (MPG) is the US standard for vehicle fuel economy: total miles driven divided by gallons of fuel consumed over that distance. To measure your real-world MPG, fill the tank to full, reset the odometer (or note it), drive normally for a tank or two, refill, and record both the miles driven since the last fill and the gallons added. Divide miles by gallons.

Real-world MPG usually trails the EPA sticker number by 5-15%, especially for hybrids and small turbo engines that perform best in EPA test conditions. Driving habits matter most: aggressive acceleration, high-speed driving (over 60 mph drag rises sharply), short trips (engines run rich until warm), and roof-rack drag all reduce MPG significantly. Smooth driving, properly inflated tires, and removing unused weight help.

For metric users, fuel economy is often expressed as L/100 km (liters per 100 kilometers — a consumption rate, not a distance rate). The conversion is L/100km = 235.215 / MPG. So 30 MPG ≈ 7.84 L/100 km, 40 MPG ≈ 5.88 L/100 km. Lower L/100km is more efficient (opposite direction from MPG).

The trip cost estimator computes how much fuel you'll burn on a given distance and what it costs at the current price per gallon. Useful for budget planning road trips, comparing the fuel cost of vehicles, or evaluating whether driving vs. flying makes more sense for a specific route.

Electric and hybrid vehicles use MPGe — miles per gallon equivalent — based on energy content (33.7 kWh per gallon-equivalent). A 100 MPGe EV uses 1/3 the energy per mile of a 33 MPG gasoline car. But the cost depends on your local electricity rate vs. gasoline price; sometimes EVs are dramatically cheaper to operate, sometimes only modestly.

Hypermilers' tricks. Drafting (very dangerous, ill-advised), coasting in neutral, pulse-and-glide, and engine-off coasting can boost MPG by 20-30% but generally aren't safe or legal. Less risky: anticipate stops, accelerate gently, and maintain steady highway speeds in the 55-65 mph range.