Gas Mileage Calculator
Calculate MPG, cost per mile & trip fuel expenses instantly
MPG & Fuel Cost
Enter miles driven and gallons used to find your miles per gallon and fuel costs.
✅ Your Results
Trip Cost Estimator
Plan ahead — estimate how much fuel will cost for an upcoming trip.
✅ Trip Estimate
What Is Gas Mileage & Why Does It Matter?
Gas mileage — commonly measured in miles per gallon (MPG) — tells you how far your vehicle can travel on a single gallon of fuel. Whether you're a daily commuter, a road-trip enthusiast, or a budget-conscious driver, knowing your MPG helps you track fuel efficiency, spot maintenance issues early, and save money at the pump.
A sudden drop in MPG can indicate under-inflated tires, a clogged air filter, or engine trouble. By regularly calculating your gas mileage, you stay informed about your vehicle's health and your spending.
How to Calculate Gas Mileage (MPG Formula)
The formula for calculating miles per gallon is refreshingly simple:
For example, if you drive 350 miles and use 14 gallons of gas, your MPG is 350 ÷ 14 = 25 MPG. Our calculator above does this instantly — and also computes your cost per mile and total fuel cost when you enter the price per gallon.
Step-by-Step Manual Calculation
- Fill up your tank completely and reset your trip odometer to zero (or note the odometer reading).
- Drive normally until you need to refuel — the more miles you cover, the more accurate the reading.
- Fill up again and note how many gallons it took to refill the tank (this is your "gallons used").
- Note the miles driven from your trip odometer (or subtract the previous odometer reading from the current one).
- Divide miles by gallons — that's your MPG!
Factors That Affect Your Gas Mileage
Many variables influence fuel economy. Understanding them can help you optimize your driving habits:
- Driving speed — Most vehicles achieve peak efficiency between 45–65 mph. Fuel economy drops sharply above 70 mph.
- Aggressive driving — Rapid acceleration and hard braking can lower MPG by 15–30% on highways.
- Tire pressure — Under-inflated tires increase rolling resistance, reducing efficiency by up to 3%.
- Vehicle load — Extra weight in the trunk or cabin forces the engine to work harder.
- Weather conditions — Cold engines run less efficiently; headwinds and winter blends of gasoline also reduce MPG.
- Air conditioning — Running AC at high settings can reduce fuel economy by 5–25%.
- Maintenance — Dirty air filters, old spark plugs, and low oil levels all hurt efficiency.
7 Proven Tips to Improve Your Gas Mileage
Average MPG by Vehicle Type
Curious how your vehicle stacks up? Here are typical MPG ranges for different vehicle categories (combined city/highway):
- Compact cars: 30–40 MPG
- Midsize sedans: 25–35 MPG
- Full-size sedans: 20–30 MPG
- Small SUVs: 22–30 MPG
- Large SUVs & trucks: 15–22 MPG
- Hybrid vehicles: 45–58 MPG
- Electric vehicles: 100+ MPGe (miles per gallon equivalent)
Frequently Asked Questions
We recommend calculating MPG every 2–3 fill-ups. Tracking it over time helps you notice trends and catch potential mechanical issues early.
Check your vehicle's official EPA rating (found on the window sticker or at fueleconomy.gov). If you're within 2–3 MPG of that number, you're in good shape.
Common culprits include under-inflated tires, a dirty air filter, faulty oxygen sensors, or a change in driving conditions (more city driving, colder weather, etc.).
This calculator uses miles and gallons (US standard). To convert, 1 US gallon ≈ 3.785 liters, and 1 mile ≈ 1.609 kilometers. For L/100km, divide 235.21 by your MPG value.
The estimate is based on the MPG and fuel price you enter. Real-world conditions (traffic, terrain, weather) may cause slight variations, but it provides a reliable ballpark figure for budgeting.
⚠️ Disclaimer: This calculator provides estimates for informational purposes only. Actual fuel consumption may vary based on driving conditions, vehicle condition, and other factors.
