Unit Conversion
Gas Mileage Calculator
Free gas mileage calculator to find your miles per gallon (MPG) and estimate trip fuel cost. Perfect for road trip planning and tracking average MPG over time.
Total distance traveled for this tank/trip
Amount of fuel used over that distance
Used to estimate total fuel cost and cost per mile
Your Fuel Economy
Fuel Economy 0
Distance 0
Fuel Used 0
Efficiency Benchmark Comparison
What MPG did I get, and what did this trip cost?
US fuel economy is miles per US gallon: miles driven ÷ gallons pumped. Optional fuel price turns that into trip cost. This page uses US gallons, not UK imperial gallons (those are bigger).
Fill-up method
- Reset trip meter at a full tank, fill to full next time, divide miles by gallons on the pump.
- Short city loops look worse than highway tanks — that is the car, not the math.
- Related: commute cost folds in days per week and wear.
Frequently Asked Questions
How do I calculate miles per gallon?
Divide the total miles driven by the gallons of fuel used: MPG = Miles ÷ Gallons. For example, if you drove 300 miles and used 10 gallons of fuel, your fuel economy is 300 ÷ 10 = 30 MPG.
How can I use this as a gas mileage calculator for a road trip?
Fill your tank at the start of your trip and note the odometer reading. When you refuel, enter the miles driven since the last fill-up and the gallons it took to refill the tank. The calculator will show your MPG for that leg of the trip, plus an estimated fuel cost if you enter a price per gallon.
How do I calculate fuel cost for a trip?
Multiply the gallons of fuel you'll use by the price per gallon: Fuel Cost = Gallons × Price per Gallon. If you know your car's MPG, you can also estimate gallons needed as Trip Distance ÷ MPG, then multiply by the price per gallon.
What is a good average MPG for a car?
It varies widely by vehicle type. Compact and hybrid cars often average 35-50+ MPG, midsize sedans typically get 25-35 MPG, and larger SUVs or trucks often average 15-25 MPG. Check your vehicle's EPA fuel economy rating for a more precise baseline.
Does this calculator work for liters and kilometers too?
This calculator is set up for miles and gallons (the standard fuel economy units in the US). If your vehicle's dashboard shows liters per 100 km, you'll need to convert those figures to miles and gallons first, or think of MPG conversion as a separate metric system calculation.
Why does my MPG vary between fill-ups?
Fuel economy fluctuates due to driving style, terrain (hills vs. flat roads), traffic conditions, weather, tire pressure, vehicle load, and whether you're driving mostly highway or city miles. Tracking multiple fill-ups and averaging them gives a more reliable picture than a single tank.
How do I estimate fuel cost before a long road trip?
Estimate your trip distance, divide by your car's average MPG to get gallons needed, then multiply by the current price per gallon along your route. This calculator's MPG comparison table shows gallons needed and cost across a range of MPG values, which is handy for planning.
Can I use this calculator to compare two vehicles?
Yes. Run the calculation separately for each vehicle's miles-driven and gallons-used figures, then compare the resulting MPG and estimated fuel costs side by side to see which is more fuel-efficient or cost-effective for your typical driving.
Related Calculators
About these results: Figures are for planning only. Confirm anything you will buy, bill, or submit (materials, payroll, medical screening) against the label, a quote, or a professional.