Gas Mileage Calculator
Gas Mileage Calculator
Gas mileage (also known as fuel economy) refers to how far your vehicle can travel per unit of fuel consumed. It is usually measured in miles per gallon (MPG) in the U.S. or kilometers per liter (km/L) in metric units.
A higher MPG or km/L means your car is using fuel more efficiently — saving you money and reducing your carbon footprint.
How to Calculate Gas Mileage:
Calculating your vehicle’s gas mileage is simple. Use our Gas Mileage Calculator above or do it manually using this formula:
Gas Mileage = (Current Odometer Reading – Previous Odometer Reading) ÷ Fuel Added
Example:
If you drove 300 miles and used 10 gallons of fuel, your gas mileage is:300 ÷ 10 = 30 MPG
Our calculator automatically performs this calculation for you and even gives the result in MPG, km/L, and L/100 km, along with an optional cost per mile if you enter your gas price.
Why Gas Mileage Matters
Improving your gas mileage has several benefits:
Save Money: Get more distance for every gallon of gas.
Reduce Emissions: Lower carbon output contributes to a cleaner environment.
Extend Vehicle Life: Efficient driving reduces engine strain and wear.
Improve Trip Planning: Know your average fuel consumption for long drives.
Top 7 Ways to Improve Your Fuel Efficiency (MPG)
Optimizing your driving and vehicle condition can yield significant returns in fuel economy, with some tips potentially improving your gas mileage by up to 40% in city driving.
1. Mind Your Driving Speed & Consistency
The speed at which you drive is one of the biggest factors affecting fuel consumption. The U.S. Department of Energy suggests that for most gasoline vehicles, the optimal speed for fuel economy is around 55 MPH (90 km/h).
| Speed Relative to Optimal 55 MPH | Efficiency Loss (Approx.) |
| 60 MPH (97 km/h) | 3% less efficient |
| 65 MPH (105 km/h) | 8% less efficient |
| 70 MPH (113 km/h) | 17% less efficient |
| 80 MPH (129 km/h) | 28% less efficient |
Use Cruise Control: On long, straight highway stretches, maintaining a constant speed with cruise control prevents unnecessary acceleration and deceleration, boosting fuel efficiency.
Avoid Aggressive Driving: Aggressive acceleration and hard braking can reduce gas mileage by roughly 15% to 30% at highway speeds and 10% to 40% in stop-and-go traffic. Drive smoothly and anticipate traffic to coast to a stop.
2. Maintain Correct Tire Pressure
Under-inflated tires increase rolling resistance, forcing your engine to work harder. Fuel economy can drop by 0.3% for every 1 PSI drop below the recommended pressure. Check your owner’s manual or the sticker on the driver’s side door jamb for the optimal PSI range. Also, ensure your wheels are properly aligned.
3. Perform Routine Vehicle Maintenance
A well-maintained engine is an efficient engine.
Motor Oil: Using the manufacturer-recommended motor oil (e.g., if it says 10W-30, don’t use 5W-30) can improve gas mileage by 1% to 2%.
Engine & Sensors: Keep your engine properly tuned and ensure the oxygen sensor is functioning; fixing a faulty O2 sensor alone can improve mileage by as much as 40%. Regularly check and replace clogged air filters to ensure proper airflow.
4. Reduce Unnecessary Weight
The heavier your vehicle, the more fuel is required to move it. Remove heavy items from your trunk or cabin that aren’t needed for your everyday commute. Even small vehicles can see a noticeable impact from excess weight.
5. Minimize Aerodynamic Drag
Drag (wind resistance) significantly impacts fuel efficiency, especially at higher speeds.
Windows: On the highway, roll up your windows. While running the air conditioning does consume fuel, the drag from open windows at high speeds can often be less efficient.
Roof Racks: Remove roof racks or bike racks when not in use, as they add both weight and substantial drag.
6. Manage Air Conditioning (AC) Use
The AC system is a major energy consumer. Fuel economy can drop by up to 25% in very hot climates due to AC usage. Limit your AC use when idling, as AC systems are generally more efficient when the car is moving.
7. Avoid Unnecessary Idling
A vehicle gets 0 MPG while idling. If you anticipate being stopped for more than 60 seconds, turning off your engine is generally more fuel-efficient than letting it run, though this should be balanced with safety and traffic conditions.
Beyond Driving: Other Fuel-Saving Strategies:
For the best possible fuel efficiency, consider alternatives:
Fuel-Efficient Vehicle: Choose a vehicle with a higher EPA fuel economy rating. Four-wheel drive (4WD) vehicles typically have lower fuel efficiency than Front-Wheel Drive (FWD) or Rear-Wheel Drive (RWD) due to the extra work required to power all four wheels.
Commuting Alternatives: Carpooling, taking public transport, walking, or bicycling eliminate fuel consumption entirely, providing the ultimate fuel efficiency.
By consistently tracking your MPG with this calculator and applying these fuel-saving tips, you’ll not only save money on gas and maintenance but also contribute to a positive environmental impact by reducing emissions.
For a comprehensive comparison of fuel efficiency across different vehicle models, and to find the EPA estimates for your car, please visit the U.S. Department of Energy’s Official Fuel Economy Website
Related Calculators:
Gas mileage, commonly measured in Miles Per Gallon (MPG) in the US or Kilometers Per Liter (km/L) in metric systems, is a measure of your vehicle’s fuel efficiency—the distance it can travel per unit of fuel consumed.
It is calculated by the simple formula: Distance Traveled / Fuel Used. To track it manually, subtract your previous odometer reading from your current reading, and then divide that distance by the amount of fuel (in gallons or liters) you added to your tank.
“Good” gas mileage depends heavily on the vehicle type (e.g., sedan, SUV, truck, or hybrid). For a modern, non-hybrid passenger car, a combined MPG of 29 to 33 MPG or higher is generally considered decent to good fuel economy. However, the most important benchmark is consistently improving your own vehicle’s calculated MPG through better maintenance and driving habits.
Generally, driving at a steady, moderate speed saves the most gas. According to the U.S. Department of Energy, most cars achieve their optimal fuel efficiency around 55 MPH (90 km/h). Fuel economy decreases rapidly above this speed. For example, driving at 70 MPH can be up to 17% less efficient than driving at 55 MPH. Use cruise control on the highway to maintain a constant, fuel-efficient speed.
Aggressive driving—which includes rapid acceleration and sudden, hard braking—significantly lowers fuel efficiency. This stop-and-go driving style forces the engine to burn more fuel to regain momentum. Adopting steady and consistent acceleration and braking habits can improve your gas mileage by 15% to 30% on highways and 10% to 40% in city traffic.
Absolutely. Proper maintenance is one of the easiest ways to improve your MPG and avoid costly repairs:
Tire Pressure: Keeping tires inflated to the recommended pressure can improve mileage by up to 3.3%.
Motor Oil: Using the manufacturer’s recommended grade of motor oil can boost efficiency by 1-2%.
Oxygen Sensor: Fixing a faulty oxygen sensor, which regulates the fuel-air mixture, can improve gas mileage by as much as 40%.
Yes, both can reduce your fuel efficiency, but one is usually worse at high speeds.
Open Windows: At highway speeds, open windows create significant aerodynamic drag, forcing your engine to work much harder to maintain speed.
Air Conditioning (AC): Running the AC draws power from the engine, which can reduce fuel economy by up to 25% in hot climates.