Gas Mileage Calculator
Compute miles per gallon (MPG) from miles driven and gallons of fuel used. Compare to EPA-published sticker MPG to see your real-world efficiency.
Last updated: September 2026
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About this calculator
Fuel economy in miles per gallon (MPG) is the standard US measure of how efficiently a vehicle turns gasoline into miles of travel. It is simply miles driven divided by gallons of fuel used between two fill-ups. Compute it by filling up, resetting your trip meter, driving as normal, and filling up again — the pump tells you the gallons and your trip meter tells you the miles.
Compare your real-world number to the EPA sticker MPG the vehicle was rated at. Real-world MPG is typically 10–20% lower than the sticker because the EPA cycles assume smooth, unaggressive driving in moderate weather. Cold weather, hard acceleration, high highway speeds (drag is quadratic in speed), roof cargo, and low tire pressure all degrade MPG.
For international comparison, Europe uses litres per 100 km (L/100 km), which is an inverse — smaller numbers are better. Rough conversion: L/100 km ≈ 235 / MPG. A 30 MPG car uses about 7.8 L/100 km.
How to use
Example — a tank-to-tank measurement. You drove 300 miles between fill-ups and pumped 10 gallons to refill. Enter miles = 300, gallons = 10. Result = 300 / 10 = 30 MPG. That is decent for a modern midsize sedan; below-average for a compact, above-average for a full-size SUV. Example — hybrid check. 450 miles on 9 gallons. Result = 50 MPG, right at the sticker for a common hybrid sedan. If your hybrid consistently comes in at 40 MPG or less when the sticker says 50, look at tire pressure, air filter, and driving style before assuming the car is broken.
Frequently asked questions
How is EPA sticker MPG measured?
The EPA runs a set of standardized driving cycles (city, highway, high-speed, air-conditioning-on, cold-weather) on a dynamometer. The published city/highway/combined numbers are weighted averages of those cycles. Modern methodology (post-2008 revision) is closer to real-world driving than the old cycles, but still tends to be optimistic — typical real-world numbers run 5–15% below sticker.
Why does MPG drop in winter?
Several factors: cold engines run rich until they warm up (10–20% lost on short trips), winter gasoline blends have slightly lower energy density, tires roll less efficiently at low pressure and low temperature, and drag increases as air density rises. Short winter trips can lose 15–30% MPG compared to summer highway driving of the same car.
How much does driving style matter?
A lot. Aggressive acceleration and hard braking can drop MPG by 25–33%. Steady speeds and gentle inputs help — cruise control on flat highway helps by a few MPG. The single biggest gain is slowing down: at 80 mph drag consumes roughly twice as much power as at 60 mph, and most modern cars are optimized for 55–65 mph.
How do I compare gas cars to electric cars?
The EPA rates electric cars in MPGe (miles per gallon equivalent), converting kWh of electricity to gasoline energy at 33.7 kWh/gal. A 3 mi/kWh EV is rated at 101 MPGe. For cost comparison, use /en/calculators/automotive/fuel-cost-calculator/ with the electricity rate you actually pay ($/kWh) rather than MPGe.