Use our Gas Mileage Calculator to quickly find your vehicle's fuel efficiency in multiple formats: miles per gallon (MPG), kilometers per liter (km/L), and liters per 100 kilometers (L/100km). Enter your trip distance and the fuel you used—optionally add fuel price to estimate trip cost and cost per mile or kilometer.
What is gas mileage and why it matters
Gas mileage describes how efficiently your vehicle converts fuel into distance traveled. Higher efficiency means you drive farther on the same amount of fuel, saving money and reducing emissions. In the United States, efficiency is usually expressed as miles per gallon (MPG), while many other regions use liters per 100 kilometers (L/100km) or kilometers per liter (km/L). Understanding all three lets you compare vehicles, plan budgets, and benchmark improvements from maintenance or driving style changes.
How to use the Gas Mileage Calculator
- Enter the total distance you traveled and choose the correct distance unit (miles or kilometers).
- Enter the total fuel you used and select the matching fuel unit (gallons or liters).
- Optionally, add the fuel price per the same unit you selected (price per gallon or per liter) and pick a currency to estimate costs.
- Click Calculate to see MPG, km/L, L/100km, and cost metrics (if price is provided).
MPG vs L/100km explained
MPG increases with efficiency—the higher the number, the better. L/100km works the opposite way—the lower the number, the better. To compare the two, remember they’re reciprocal after unit conversion. Our calculator handles the conversions automatically so you can see all common measures at once.
What the results mean
- MPG (US): Miles driven per US gallon of fuel. Useful for US-based comparisons and EPA ratings.
- km/L: Kilometers driven per liter of fuel. Common in many countries and helpful for quick mental math.
- L/100km: Liters required to travel 100 km. Favored in Europe and Canada for its linear relationship with fuel consumption.
- Cost per mile/km: Shows how much you spend for each unit of distance, based on the price per gallon or per liter you provide.
Tips to improve your gas mileage
- Maintain steady speeds and anticipate traffic to reduce harsh acceleration and braking.
- Keep tires properly inflated and aligned to minimize rolling resistance.
- Remove unnecessary cargo and roof racks to cut weight and aerodynamic drag.
- Follow recommended maintenance: air filters, spark plugs, and oil changes.
- Use cruise control on highways when conditions allow.
- Avoid excessive idling and combine errands to reduce cold starts.
Frequently used conversions
- 1 mile = 1.609344 kilometers
- 1 kilometer = 0.621371 miles
- 1 US gallon = 3.785411784 liters
- 1 liter = 0.264172 US gallons
Why this Gas Mileage Calculator helps
Real-world fuel economy can differ from window-sticker ratings due to driving style, weather, terrain, and vehicle condition. This Gas Mileage Calculator uses your own trip data, so you see results tailored to your route and habits. By tracking results over time, you can confirm whether changes—like new tires or a different commute—make a difference. Add fuel prices to turn efficiency into actionable costs, revealing how much each mile or kilometer truly costs and helping you budget smarter.
Pro tip: measure accurately
For consistent results, use the full-tank method: fill your tank, reset your trip meter, drive normally, then refill and record exact distance and fuel added. Repeat a few times and average the results to smooth out variations from traffic, weather, and pump shutoff differences. Our calculator will convert and summarize the metrics for you every time.