Calculate Gas Mileage

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Gas Mileage Calculator

Calculate your vehicle's fuel efficiency and trip costs

Fuel Efficiency
0 MPG
Distance Driven
0 Miles
Cost Per Mile
$0.00
Total Trip Cost
$0.00

Understanding Your Vehicle's Fuel Efficiency

Knowing your vehicle's gas mileage is one of the most effective ways to track car health and manage your travel budget. Gas mileage, typically measured in Miles Per Gallon (MPG), indicates how far your vehicle can travel for every gallon of fuel consumed.

How to Calculate Gas Mileage Manually

If you don't have this calculator handy, you can follow these simple steps during your next fuel stop:

  1. Fill your tank completely and record your current odometer reading (Starting Miles).
  2. Drive as you normally would until you need more fuel.
  3. Fill the tank completely again and record two things: the new odometer reading (Ending Miles) and the exact number of gallons it took to refill the tank.
  4. Subtract the Starting Miles from the Ending Miles to get your total distance driven.
  5. Divide the distance driven by the number of gallons added.

Example Calculation:

Start: 50,000 miles | End: 50,300 miles | Gallons: 10
Distance: 50,300 – 50,000 = 300 miles
MPG: 300 / 10 = 30 MPG

Factors That Affect Your MPG

  • Driving Habits: Rapid acceleration and heavy braking significantly reduce efficiency.
  • Tire Pressure: Under-inflated tires increase rolling resistance, forcing the engine to work harder.
  • Vehicle Weight: Carrying unnecessary heavy items in the trunk or using roof racks increases drag and weight.
  • Maintenance: Old spark plugs, dirty air filters, or clogged fuel injectors can lower your fuel economy.
  • Idling: Letting your car run while stationary yields 0 MPG and wastes significant fuel over time.
function calculateGasMileage() { var startMiles = parseFloat(document.getElementById('startMiles').value); var endMiles = parseFloat(document.getElementById('endMiles').value); var fuelUsed = parseFloat(document.getElementById('fuelUsed').value); var gasPrice = parseFloat(document.getElementById('gasPrice').value); var resultsDiv = document.getElementById('mileageResults'); // Validation if (isNaN(startMiles) || isNaN(endMiles) || isNaN(fuelUsed) || fuelUsed <= 0) { alert('Please enter valid numbers for odometer readings and fuel used.'); return; } if (endMiles 0) { var totalCost = fuelUsed * gasPrice; var costPerMile = totalCost / distance; document.getElementById('totalCostResult').innerText = '$' + totalCost.toFixed(2); document.getElementById('costPerMileResult').innerText = '$' + costPerMile.toFixed(2); } else { document.getElementById('totalCostResult').innerText = 'N/A'; document.getElementById('costPerMileResult').innerText = 'N/A'; } // Smooth scroll to results on mobile resultsDiv.scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }

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