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
Processed on our server. What you enter is sent over an encrypted connection, calculated, and returned. It is never written to a database or logged, and nothing is retained once the result is sent. Avoid entering passwords, API keys or other secrets. How we handle data
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.