MPG Calculator — Gas Mileage Guide ()
Knowing your car's actual MPG helps you budget for fuel, compare vehicles, plan road trips, and decide whether a more fuel-efficient car makes financial sense. The EPA estimates on window stickers are tested under ideal conditions — your real-world MPG typically runs 10–20% lower depending on driving habits, terrain, and traffic.
How to Calculate MPG
The formula is simple: MPG = Miles Driven ÷ Gallons Used. For the most accurate reading, fill your tank completely, reset your trip odometer to zero, drive normally, then fill up completely again. The gallons it takes to refill is your denominator. Most drivers average this over several fill-ups for a more representative number.
Average MPG by Vehicle Type ()
| Vehicle Type | City MPG | Highway MPG | Combined MPG | Annual Fuel Cost* |
|---|
| Compact Car (gas) | 28–32 | 36–42 | 30–36 | $1,100–$1,400 |
| Midsize Sedan | 24–28 | 32–38 | 27–32 | $1,300–$1,600 |
| Full-size Sedan | 20–25 | 28–34 | 23–28 | $1,500–$1,900 |
| Small SUV / Crossover | 24–28 | 30–36 | 26–31 | $1,400–$1,700 |
| Midsize SUV | 18–23 | 24–30 | 20–26 | $1,700–$2,200 |
| Full-size SUV / Truck | 14–18 | 18–24 | 16–20 | $2,200–$2,800 |
| Hybrid (compact) | 48–55 | 44–52 | 47–53 | $800–$950 |
| Hybrid (midsize) | 40–48 | 38–45 | 40–46 | $950–$1,100 |
| Plug-in Hybrid | 30–40 MPGe | — | — | $500–$900 |
| Electric Vehicle | 100–130 MPGe | — | — | $400–$700 |
*Based on 12,000 miles/year at $3.50/gallon. Actual costs vary.
Tips to Improve Your Gas Mileage
Small changes in driving habits can improve real-world MPG by 10–30%, saving hundreds of dollars per year. Tire pressure alone accounts for up to 3% of fuel economy — underinflated tires create rolling resistance. Speed matters significantly: fuel economy drops sharply above 55 mph, with each 5 mph over 50 costing about 7–14% more fuel. Idling gets 0 MPG — turning off the engine during stops longer than 60 seconds saves measurable fuel. Smooth acceleration and braking vs. aggressive driving can save 15–30% in city driving.
How do I calculate my MPG?
Fill your tank completely and note your odometer reading (or reset your trip meter). Drive normally until your tank is low, then fill up completely again. Divide the miles driven by the gallons it took to refill. For example: if you drove 350 miles and used 12 gallons, your MPG is 350 ÷ 12 = 29.2 MPG. For the most accurate result, average this over 3–4 fill-ups rather than relying on a single calculation.
What is a good MPG for a car?
A good MPG depends on the vehicle type. For a regular gas-powered car, 30+ MPG combined is considered good, 35+ is very good, and 40+ is excellent. For SUVs and trucks, 25+ combined is good. The national average for new cars in the US is around 26–28 MPG combined. Hybrids typically achieve 40–55 MPG, while electric vehicles are rated in MPGe (miles per gallon equivalent) and typically show 100–130 MPGe.
How much does 1 MPG improvement save per year?
The savings depend on your current MPG and how many miles you drive. At 12,000 miles/year and $3.50/gallon, improving from 25 MPG to 26 MPG saves about $65/year. Improving from 20 to 21 MPG saves about $100/year (more dramatic at lower MPG). The savings from poor MPG to good MPG are substantial: going from 15 MPG to 30 MPG saves $1,400/year at those same assumptions — literally doubling your fuel economy cuts your fuel bill in half.
Why is my actual MPG lower than the EPA estimate?
EPA fuel economy tests are conducted on a dynamometer (rollers) in a lab under controlled conditions — no wind resistance, consistent temperature, no hills, no traffic. Real-world driving includes all of these variables. Aggressive acceleration, air conditioning use, highway speeds over 65 mph, cold weather (which thickens fluids and requires longer warm-up), carrying extra weight, and city stop-and-go traffic all reduce real MPG. A reasonable expectation is 10–20% below EPA estimates for most drivers, though hypermilers can sometimes beat EPA ratings.
Is it worth buying a more fuel-efficient car?
Use the Compare Cars tab above to calculate exact savings for your situation. As a general rule, the higher your annual mileage and the more your current car differs in MPG from the new one, the faster the fuel savings pay back any price premium. At 15,000 miles/year and $3.50/gas, going from 22 MPG to 35 MPG saves about $900/year in fuel. Over 5 years that's $4,500 in fuel savings — which may offset part of the price difference of a more efficient vehicle, not counting lower maintenance costs for hybrids and EVs.
How do I calculate the fuel cost for a road trip?
Use the Trip Cost tab above. Enter your trip distance, your car's MPG, and the current gas price. The formula is: Trip Fuel Cost = (Distance ÷ MPG) × Gas Price. For a 500-mile trip in a car that gets 30 MPG at $3.50/gallon: (500 ÷ 30) × $3.50 = $58.33 one way, or $116.67 round trip. Don't forget that highway driving typically delivers better MPG than city driving, so your road trip MPG may be higher than your usual combined average.