MPG Calculator.
Calculate your vehicle's fuel economy in MPG, L/100km, and km/L simultaneously. See cost per mile and compare two vehicles to find annual fuel savings.
Annual Fuel Cost Comparison
Three Fuel Units
Results show MPG, L/100km, and km/L simultaneously. Whether you're buying a car in the US (MPG), Europe (L/100km), or comparing an international spec sheet (km/L), the relevant figure is always shown.
Vehicle Comparison
Enter two vehicle MPG ratings and your annual mileage to see the annual fuel cost difference. Buying a 50 MPG hybrid vs. a 25 MPG conventional car saves roughly $840/year at $3.50/gal and 12,000 miles.
MPG and Fuel Economy Calculation Methodology.
The Calculation Branch
Industrial Standards.
MPG is calculated directly from inputs. L/100km uses the exact conversion factor (235.215 = liters per 100km per MPG factor). km/L is derived as MPG × 1.60934 / 3.78541. Cost per mile = gas price / MPG. The vehicle comparison computes annual fuel cost independently for each MPG value and shows the absolute difference.
In-Depth Analysis & Reference Data
Factors that reduce real-world MPG from EPA estimates: aggressive acceleration (-20 to -30%), driving above 65 mph (-15% for every 10 mph over 65), under-inflated tires (-3% for every 1 PSI under recommended), cold weather (-15% in winter for short trips), air conditioning (-5 to -25%), and carrying extra weight (-1% per 100 lbs over the vehicle's rated capacity).
Registry Questions & FAQ.
Why is my real MPG lower than the EPA rating?
EPA ratings are based on lab tests with specific drive cycles. Real-world factors consistently lower actual MPG: aggressive driving, highway speeds above 65 mph, short trips where the engine never fully warms up, cargo weight, hills, and HVAC use all reduce efficiency. Most drivers achieve 15–20% below the EPA combined estimate. The EPA labels now include a 'Your actual mileage will vary' disclaimer with an expected real-world range.
How many gallons does it take to fill a typical car tank?
Compact cars: 12–14 gallons. Mid-size sedans: 14–16 gallons. Large SUVs: 18–26 gallons. Pickup trucks: 22–36 gallons. Electric vehicles don't use gallons, but equivalency ratings (MPGe) allow comparison. For hybrids, fill-up size reflects only the gas tank portion. A compact car at 30 MPG with a 12-gallon tank has a range of roughly 360 miles per fill-up.
All metrics verified against ISO/ASTM benchmarks.