Gas Mileage Calculator

Fuel Economy
30.0 MPG
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⛽ Cost Projections

Cost for This Trip–
Cost Per Mile–
Cost for Other Trip–

What Is a Gas Mileage Calculator?

A gas mileage calculator computes your vehicle's fuel economy in miles per gallon (MPG) based on distance traveled and fuel used, and projects fuel costs for any trip distance using your current gas price.

How to Use the Gas Mileage Calculator

  1. Enter the distance you traveled.
  2. Enter how many gallons of fuel that trip used.
  3. Enter your current price per gallon.
  4. Enter any other trip distance to project its fuel cost.

Gas Mileage Formula

Fuel Economy
MPG = Miles Driven ÷ Gallons Used
Trip Cost
Cost = (Trip Distance ÷ MPG) × Price Per Gallon

Worked Example

Example: 300 Miles on 10 Gallons

MPG = 300 ÷ 10 = 30.0 MPG

Cost per mile: $3.50 ÷ 30 ≈ $0.117/mile

Cost for a 500-mile trip: (500 ÷ 30) × $3.50 ≈ $58.33

Understanding Your Results

Fuel Economy (MPG) measures how efficiently your vehicle uses fuel. Cost Per Mile and trip cost projections use that MPG figure with your local gas price to estimate what any trip will cost in fuel.

Tips for Improving Gas Mileage

  • Keep tires properly inflated — underinflated tires increase rolling resistance and reduce MPG.
  • Avoid aggressive acceleration and braking, which burns noticeably more fuel.
  • Remove excess weight and roof cargo when not needed, both of which reduce efficiency.
  • Keep up with regular maintenance, including air filter and spark plug replacement.

Common Mistakes to Avoid

  • Calculating MPG from a single fill-up without resetting the trip odometer, which can skew results.
  • Not accounting for how highway vs. city driving affects fuel economy differently.
  • Using an outdated gas price for cost projections — check current local prices for accuracy.

Frequently Asked Questions

Divide the total miles driven by the gallons of fuel used to travel that distance.

Fill your tank completely, reset your trip odometer, drive until you need to refill, then divide the miles driven by the gallons needed to refill to full.

Driving conditions (highway vs. city), terrain, weather, driving style, and vehicle load all affect fuel economy from one tank to the next.

Divide your planned trip distance by your vehicle's MPG, then multiply by the current price per gallon — this calculator does that automatically.

Generally yes, assuming the same fuel price — higher MPG means less fuel is needed to cover the same distance, directly lowering cost per mile.