Compare MPG: Calculate MPG, Trip Fuel Cost, and Compare Vehicles Side-By-Side

Trip Cost and MPG Calculator

Fill in any two of the first three fields to instantly calculate the third. MPG (Miles Per Gallon) tells you how far your vehicle travels on a single gallon of fuel. A higher MPG means better fuel efficiency and lower costs.

Distance Driven What is this? How many miles did you (or will you) drive?

Gallons of Fuel Used What is this? Check your fill-up receipt for this number.

Price Per Gallon ($) What is this? Check the sign at your nearest gas station.

Calculated MPG

miles per gallon

Total Trip Cost

US dollars

Cost Per Mile

dollars per mile

Results update automatically as you type. MPG is calculated from Distance and Gallons. Trip Cost is calculated from Gallons and Price Per Gallon.

Side-By-Side Vehicle Comparison

Enter the MPG and fuel price for two vehicles to compare their annual operating costs. "Annual Mileage" is how many total miles you drive per year - the US average is about 14,000 miles.

Estimated Annual Mileage What is this? US average: ~14,000 miles/year. Adjust to your own driving habits.

Vehicle A

Vehicle Label (optional) e.g. "2023 Honda Civic" or "Current Car"

Average MPG What is this? Find EPA estimates at fueleconomy.gov or check your window sticker.

Fuel Price Per Gallon ($) Use regular unleaded, premium, or diesel price as applicable.

Annual Fuel Cost

per year

Vehicle B

Vehicle Label (optional) e.g. "2024 Toyota Camry Hybrid" or "New Car"

Average MPG What is this? Find EPA estimates at fueleconomy.gov or check your window sticker.

Fuel Price Per Gallon ($) Hybrids still use gasoline; EVs use electricity (kWh cost) instead.

Annual Fuel Cost

per year

Enter MPG and fuel price for both vehicles to see your annual savings comparison.

The Ultimate Guide to Fuel Economy, MPG, and Trip Planning

Whether you are shopping for a new vehicle, trying to stretch your gas budget, or simply curious about how fuel economy works, this guide breaks down everything you need to know in plain language - complete with the real math behind the numbers.

How do you calculate your actual MPG manually? +

MPG - short for Miles Per Gallon - is the single most important number for understanding your vehicle's fuel efficiency. It tells you how many miles your car can travel on one gallon of gasoline. The higher the number, the more efficient the vehicle and the less you spend on fuel.

To measure your own real-world MPG accurately, follow this process:

Fill your tank completely until the pump clicks off.
Reset your trip odometer to zero (or note your current odometer reading).
Drive normally until your tank is low, then fill up again completely.
Record the number of gallons it took to refill the tank and the miles driven.

The formula is straightforward:

MPG = \frac{\text{Miles Driven}}{\text{Gallons Used}}

For example, if you drove 320 miles and used 11.5 gallons to refill: $MPG = 320 \div 11.5 \approx 27.8$ miles per gallon.

This real-world MPG will almost always differ from the official EPA Estimate (the number on a vehicle's window sticker). EPA testing is done under controlled laboratory conditions, so real-world driving - with traffic, hills, air conditioning, and varying speeds - typically reduces efficiency by 10 to 20 percent.

What is the fuel cost formula and how is trip cost calculated? +

Once you know your MPG and the current price of gas, calculating the cost of any trip is simple algebra. The core formula used by this calculator is:

\text{Trip Cost} = \left( \frac{\text{Distance (miles)}}{\text{MPG}} \right) \times \text{Price Per Gallon}

The first part of the equation, $\frac{Distance}{MPG}$, gives you the number of gallons your trip will consume. Multiplying that by the price per gallon converts gallons into dollars.

Example: A 400-mile road trip in a vehicle averaging 28 MPG, with gas at $3.60 per gallon:

\text{Trip Cost} = \left( \frac{400}{28} \right) \times 3.60 = 14.29 \times 3.60 \approx \$51.43

The Annual Fuel Cost formula used in Mode 2 of this calculator applies the same logic over an entire year:

\text{Annual Fuel Cost} = \left( \frac{\text{Annual Mileage}}{\text{MPG}} \right) \times \text{Price Per Gallon}

The Price Per Gallon used in these calculations is a static snapshot - it does not adjust for future price changes. For long-range financial planning, consider averaging several months of local gas prices together to get a more realistic annual cost estimate.

Why does city driving get worse gas mileage than highway driving? +

This is one of the most common questions about fuel economy, and the answer comes down to physics. When your car sits at a red light or crawls in traffic, the engine is still running - burning fuel to idle and power accessories - while moving zero miles. This is pure waste from an MPG perspective.

Highway driving, by contrast, lets you cruise at a steady speed. Modern engines are most efficient when operating at a consistent throttle position, which is exactly what highway cruising provides. Frequent stopping and starting forces the engine to repeatedly accelerate the full weight of the car from rest, which is extremely energy-intensive.

This is why EPA window stickers show two separate figures - a City MPG and a Highway MPG. A typical midsize sedan might show 26 MPG city and 36 MPG highway. The Combined MPG (the most commonly quoted figure) is a weighted average that assumes approximately 55 percent city and 45 percent highway driving, reflecting a typical American's driving mix.

Hybrid vehicles narrow this gap dramatically. Their regenerative braking systems capture energy that would otherwise be lost as heat every time you slow down, and their electric motors handle low-speed acceleration efficiently. This is why hybrids often achieve their best fuel economy in stop-and-go city traffic - the opposite of gasoline-only vehicles.

Are hybrid vehicles always more cost-effective? Understanding the break-even point. +

Hybrids are almost always more fuel-efficient, but "more fuel-efficient" does not automatically mean "more cost-effective." The key concept is the Break-Even Point - the number of years it takes for cumulative fuel savings to offset the higher upfront purchase price of the more efficient vehicle.

\text{Break-Even (years)} = \frac{\text{Price Difference}}{\text{Annual Fuel Savings}}

Example: A hybrid costs $4,000 more than its gasoline equivalent but saves $700 per year in fuel. The break-even point is $4000 \div 700 \approx 5.7$ years. If you plan to keep the vehicle longer than that, the hybrid wins financially. If you trade in after three years, the gasoline version may be cheaper overall.

Several factors can shift this calculation significantly:

Gas prices: Higher fuel prices accelerate the break-even point in the hybrid's favor.
Annual mileage: High-mileage drivers save more fuel per year, reaching break-even faster.
Depreciation: Hybrids sometimes retain resale value better, improving their long-term economics.
Incentives: Federal and state tax credits can reduce the effective price difference significantly.
Maintenance: Hybrids generally have lower brake maintenance costs due to regenerative braking, though battery replacement (if needed after 150,000 to 200,000 miles) is a significant expense.

Use the Mode 2 comparison above with the optional price difference field to calculate the exact break-even point for any two vehicles you are considering.

How do tire pressure, driving habits, and maintenance affect fuel economy? +

Your vehicle's EPA estimate is a theoretical best case measured under optimal conditions. Real-world fuel economy is a moving target influenced by dozens of controllable variables. Understanding them can help you meaningfully improve your MPG without spending a dollar.

Tire Pressure: Under-inflated tires increase rolling resistance - the friction between the tire and the road. The US Department of Energy estimates that for every 1 PSI drop below the recommended pressure across all four tires, fuel economy decreases by approximately 0.2 percent. Tires that are 10 PSI low can reduce MPG by 2 to 3 percent. Check your door jamb sticker (not the tire sidewall) for the correct pressure.
Speed: Aerodynamic drag increases with the square of velocity. Driving at 75 mph instead of 65 mph can reduce fuel economy by 10 to 15 percent. The formula for aerodynamic drag force is $F_d = \frac{1}{2} \rho v^2 C_d A$, where $v$ is velocity - doubling speed quadruples drag force.
Aggressive Acceleration and Braking: Every hard acceleration burns extra fuel to push the vehicle up to speed, and every hard brake discards that kinetic energy as heat. Smooth, gradual acceleration and coasting to decelerate can improve real-world MPG by 10 to 30 percent in city driving.
Air Conditioning: A/C can reduce fuel economy by 5 to 25 percent depending on ambient temperature and system load. At highway speeds, using A/C is generally more efficient than opening windows (which increases drag); at city speeds the opposite is true.
Engine Maintenance: A clogged air filter, worn spark plugs, degraded motor oil, or a failing oxygen sensor can each reduce MPG by 2 to 10 percent individually. Regular tune-ups keep the engine running at its designed efficiency.
Cargo and Weight: Every extra 100 pounds in your vehicle reduces fuel economy by about 1 percent. Roof cargo boxes add significant aerodynamic drag at highway speeds.

Combining these improvements - properly inflated tires, moderate highway speeds, smooth driving, and regular maintenance - can realistically recover 20 to 30 percent of the gap between your real-world MPG and the EPA estimate.