350 mi / 12.5 gal
- Gallons per 100 mi
- 3.5714285714
- L/100 km
- 8.4005208214
- Miles driven
- 350
Gas Mileage Calculator
Use this free gas mileage calculator to find miles per gallon, gallons per 100 miles, and liters per 100 km from a tank or trip.
Research-backed assumptions Formula steps Examples included Private in-browser use
Formula steps
- Divide miles driven by gallons used.
- Convert the same result into gallons per 100 miles for comparison.
- Use the standard MPG to L/100 km conversion for metric comparison.
How to use the gas mileage calculator
- Enter miles driven and gallons used from the same tank or trip.
- Press Calculate gas mileage to see MPG, gallons per 100 miles, and L/100 km.
- Use the result in the Fuel Cost Calculator when estimating trip cost.
- Expect one-tank results to vary with fill level, weather, speed, and traffic.
Common uses
Calculate MPG after filling a tank.
Compare fuel use between trips or vehicles.
Convert MPG into gallons per 100 miles or L/100 km.
Use a real trip value inside the Fuel Cost Calculator.
Examples
28 MPG
About 28.06 MPG
17.5 MPG
Frequently asked questions
Plain-language answers about when to use the tool, what it does with your inputs, what to double-check, and how privacy works.
When should I use the Gas Mileage Calculator?
Use it when your task matches one of these common needs: Calculate MPG after filling a tank. Compare fuel use between trips or vehicles. It works best when you already know the values, dates, units, or settings the page asks for.
What is the Gas Mileage Calculator doing with my inputs?
In plain language: The calculator divides miles driven by gallons used to get MPG, then converts the same relationship into gallons per 100 miles and L/100 km. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.
What should I double-check before trusting the answer?
Tank fill differences, tire pressure, route, speed, weather, and driving style can change real-world fuel economy. Also check that you used the right unit, date, scale, or mode because small input changes can change the result.
Does the site save what I enter?
No. The calculator runs in your browser tab. Your recent answers stay only on the page while you use it, and they are not sent to a server.
Related tools
Fuel Cost Calculator Estimate fuel cost from distance, MPG, fuel price, and round-trip setting. Open Mileage Calculator Multiply miles by a rate per mile and add optional parking or toll costs. Open Conversion Calculator Convert length, mass, volume, and temperature units with clear formula steps. Open