Gas Mileage Calculator

Calculate your car's fuel efficiency in MPG, km/L, or L/100km. Track gas mileage and estimate annual fuel costs.

Fuel Efficiency

MPG

29.2

Miles per gallon

L/100km

8.1

Liters per 100km

km/L12.40
Cost/Mile$0.120
Annual Cost$1440

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Cost Estimation Settings

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Your Results

MPG

29.2

km/L

12.4

L/100km

8.1

You traveled 350 miles using 12 gallons of fuel.

Annual Cost Estimates

Annual Fuel Cost

$1440

at 12,000 mi/year

Annual CO₂

3.7 tons

carbon dioxide

Cost per Mile

$0.120

Cost per Kilometer

$0.075

Annual Fuel Cost by MPG

Based on 12,000 miles/year at $3.50/gallon

Your Efficiency Rating

PoorBelow AvgAverageGoodExcellent
1020304050+ MPG

Your vehicle's 29.2 MPG is Average

Tips to Improve Fuel Efficiency

  • •Keep tires properly inflated (check monthly) - can improve MPG by up to 3%
  • •Remove excess weight from your vehicle - every 100 lbs reduces MPG by 1-2%
  • •Avoid aggressive acceleration and braking - smooth driving can save 15-30%
  • •Use cruise control on highways to maintain consistent speed
  • •Drive at moderate speeds - MPG typically drops above 50 mph
  • •Keep up with regular maintenance - air filters, spark plugs, oil changes

Quick Answer

To calculate MPG: divide miles driven by gallons used. Formula: MPG = Miles Driven / Gallons Used. For example, if you drove 350 miles on 12 gallons: 350 / 12 = 29.2 MPG. For accurate results, fill your tank completely, reset trip odometer, drive normally, then fill again and note gallons added and miles driven.

Key Facts

  • MPG Formula: Miles Driven / Gallons Used = MPG
  • L/100km Formula: (Liters Used / Km Driven) x 100
  • EPA combined MPG is 55% city / 45% highway weighted
  • Actual MPG is often 10-20% lower than EPA estimates
  • City MPG is typically 20-30% worse than highway MPG
  • Every 5 mph over 50 mph costs approximately $0.25/gallon in efficiency
  • Properly inflated tires improve MPG by up to 3%
  • A clean air filter can improve MPG by up to 10%

Frequently Asked Questions

Fill your tank completely and note the odometer. Drive normally until you need fuel again. Fill up completely and note gallons used and new odometer reading. Divide miles driven by gallons used. Example: 350 miles ÷ 12 gallons = 29.2 MPG.
Driving habits (speed, acceleration, braking), tire pressure (underinflated tires reduce MPG by 0.2% per PSI), vehicle maintenance (air filters, spark plugs), weight (100 lbs reduces MPG by 1-2%), weather (cold reduces efficiency), AC use, and aerodynamics.
Depends on vehicle type. Excellent: 40+ MPG (hybrids, small cars). Good: 30-40 MPG (compact/midsize). Average: 25-30 MPG (sedans, crossovers). Below average: 20-25 MPG (SUVs, larger vehicles). Poor: under 20 MPG (trucks, older vehicles).
At $3.50/gallon and 12,000 miles/year: Improving from 25 to 30 MPG saves $80/year. From 20 to 25 MPG saves $168/year. From 30 to 40 MPG saves $150/year. Small improvements add up significantly over time.
It depends on your typical driving. EPA estimates show both. Highway MPG is typically 20-30% higher than city due to constant speeds and less braking. Most drivers get combined MPG closer to city rating. Track your actual driving for accurate numbers.