How is MPG calculated?

Miles per gallon (MPG) = miles driven ÷ gallons of fuel used. Fill your tank, drive a known distance, refill, and note how many gallons it took. Divide the miles by the gallons.

How do I convert MPG to L/100km?

Use the formula: L/100km = 235.214 ÷ MPG. For example, 30 MPG = 235.214 ÷ 30 ≈ 7.84 L/100km. This calculator computes all three metrics automatically.

Kilometers per liter (km/L) is common in Asia and Latin America. It measures how many kilometers you travel per liter of fuel. To convert km/L to MPG, multiply by 2.35214.

What is a good fuel economy?

For gasoline cars: 30+ MPG (7.8 L/100km) is good, 40+ MPG (5.9 L/100km) is excellent. Hybrids can reach 50–60 MPG. Diesel vehicles often achieve 40–50 MPG on highways.

Gas Mileage (MPG) Calculator

How to calculate MPG

Fill your tank completely, then drive a known distance. When you refill, note how many gallons it took. MPG = miles driven ÷ gallons used. For example, 300 miles on 10 gallons = 30 MPG.

Common fuel economy conversions

MPG	km/L	L/100km
20 MPG	8.50 km/L	11.76 L/100km
25 MPG	10.63 km/L	9.41 L/100km
30 MPG	12.75 km/L	7.84 L/100km
35 MPG	14.88 km/L	6.72 L/100km
40 MPG	17.01 km/L	5.88 L/100km
50 MPG	21.26 km/L	4.70 L/100km

MPG vs L/100km explained

MPG (miles per gallon) is used in the United States. A higher number means better fuel economy. L/100km (liters per 100 km) is used in most of the world; a lower number is more efficient. The two are inversely proportional: L/100km = 235.214 ÷ MPG.

Factors affecting fuel economy

Speed: most vehicles achieve peak fuel economy between 45–55 mph. Above 60 mph, aerodynamic drag increases sharply - driving at 80 mph can reduce economy by 20–30%.
Tire pressure: under-inflated tires increase rolling resistance. Maintaining proper pressure can improve MPG by 0.5–3%.
Cargo and roof racks: every 100 lbs of extra weight reduces MPG by approximately 1%. An empty roof rack increases drag by 2–8%.
Air conditioning: AC can reduce fuel economy by 5–25% in city driving, less at highway speeds.
Cold starts: engines run rich when cold, burning up to 50% more fuel for the first 1–2 miles.

Annual fuel cost calculation

Estimated annual fuel cost = (annual miles ÷ MPG) × price per gallon. At 15,000 miles/year, 30 MPG, and $3.50/gal: 15,000 ÷ 30 × $3.50 = $1,750/year. Improving to 40 MPG cuts this to $1,313 - a $437 annual saving.

MPGe for electric vehicles

The US EPA defines Miles Per Gallon equivalent (MPGe) as the number of miles an EV travels on 33.7 kWh of electricity - the energy content of one gallon of gasoline. An EV rated at 100 MPGe uses 33.7 kWh to travel 100 miles. MPGe allows direct cost comparisons between EVs and conventional vehicles.