Worked example: a 300-mile drive
- Fuel used: 300 miles ÷ 28 MPG = 10.7 gallons
- Fuel cost: 10.7 gallons × $3.50 = $37.50
- Cost per mile: $37.50 ÷ 300 = about 12.5 cents
The round trip doubles it to $75.00. Split between three people, each pays $25.00. The $3.50 is only an example, so put in the price on the sign at your station for your own number.
Gas cost by gallons and by miles
These tables use the price and fuel economy in the calculator, so they change when you change those numbers.
How much is 5 to 25 gallons of gas?
| Gallons | Cost |
|---|---|
| 5 | $17.50 |
| 10 | $35.00 |
| 12 | $42.00 |
| 15 | $52.50 |
| 18 | $63.00 |
| 20 | $70.00 |
| 25 | $87.50 |
Gas cost for 100 to 2,000 miles
| Distance | Fuel | Cost |
|---|---|---|
| 100 miles | 3.6 gal | $12.50 |
| 250 miles | 8.9 gal | $31.25 |
| 500 miles | 17.9 gal | $62.50 |
| 1,000 miles | 35.7 gal | $125.00 |
| 2,000 miles | 71.4 gal | $250.00 |
How the fuel cost is calculated
The formula
Fuel cost = distance ÷ fuel economy × price per gallon
Dividing the distance by your MPG gives the gallons the drive will burn. Multiplying by the price gives the cost. Cost per mile is the price divided by your MPG, so a car that gets 28 MPG at $3.50 a gallon spends 12.5 cents on fuel for every mile.
Using kilometers and liters
With L/100 km, the liters used are the distance in kilometers × L/100 km ÷ 100, then multiply by the price per liter. The calculator converts between systems using exact factors: 1 mile is 1.609344 km and 1 US gallon is 3.785411784 liters. To turn L/100 km into US MPG, divide 235.215 by the L/100 km figure.
Why your real cost can differ
The answer is only as good as the MPG you enter. EPA ratings come from standard lab tests, and traffic, speed, hills, cargo and weather all move the real number. If you track your own fill-ups (miles driven ÷ gallons to refill), use that figure for the closest estimate.
Cedrick Reese built this calculator after planning long drives, from Florida to Mississippi and across Europe, without a clear idea of what the fuel would cost. The math is the standard distance ÷ fuel economy × price formula, and each result is checked against hand-worked examples like the 300-mile drive above. The car picker reads EPA city, highway and combined ratings from the fueleconomy.gov vehicle dataset, and its lookup files are rebuilt whenever that dataset is refreshed. The site doesn't publish gas prices, so every dollar figure here comes from the price you enter or is marked as an example.
Fuel cost questions
How do I calculate the fuel cost for a trip?
Divide the distance by your fuel economy to get the gallons you'll use, then multiply by the price per gallon. A 300-mile drive at 28 MPG uses about 10.7 gallons, so at an example price of $3.50 a gallon it costs about $37.50.
How much will gas cost for a 1,000-mile trip?
It depends on your MPG and the price you pay. At 25 MPG you'd use 40 gallons, so at an example price of $3.50 a gallon the drive costs $140. At 35 MPG it's about 28.6 gallons, or about $100 at the same example price.
How far will $40 of gas get me?
Divide $40 by the price per gallon to get the gallons you're buying, then multiply by your MPG. At an example price of $3.50 a gallon, $40 buys about 11.4 gallons, which takes a 25 MPG car about 286 miles.
Does this calculator use today's gas prices?
No. Prices change daily and vary by station, so you enter the price you pay. For averages, AAA publishes a daily national and state average, and the U.S. Energy Information Administration publishes a weekly retail price survey.
Should I use city, highway or combined MPG?
Use highway MPG for long interstate drives, city MPG for short trips in traffic, and combined MPG when the drive is a mix. Combined is the EPA's weighted average of the two. Your own measured MPG from recent fill-ups is usually closer than any rating.
How do I convert L/100 km to MPG?
Divide 235.215 by the L/100 km figure. For example, 8 L/100 km is about 29.4 US MPG. With L/100 km a lower number means better fuel economy, which is the opposite of MPG. The calculator converts it for you when you choose L/100 km.
Price averages: AAA gas prices and EIA gasoline and diesel prices.
What changes your fuel cost
Once the distance and price are fixed, the only lever left is fuel economy. These figures come from the U.S. Department of Energy's driving tips and maintenance tips.
- Driving style. Speeding, hard acceleration and hard braking can lower gas mileage by roughly 15% to 30% at highway speeds and 10% to 40% in stop-and-go traffic.
- Roof boxes. A large roof-top cargo box can cut fuel economy by around 2% to 8% in city driving, 6% to 17% on the highway and 10% to 25% at Interstate speeds.
- Extra weight. An extra 100 pounds in the vehicle can reduce MPG by about 1%.
- Idling. An idling engine uses a quarter to a half gallon of fuel per hour, depending on engine size and AC use.
- Tire pressure. Keeping tires at the right pressure improves gas mileage by 0.6% on average, and up to 3% in some cases.
- Motor oil. Using the manufacturer's recommended grade can improve gas mileage by 1% to 2%.
More fuel tools
Not sure what MPG to enter? Look up your car's MPG by make and model on our sister site, GasMileageCalculators.com. If you're weighing two vehicles, compare their fuel costs side by side.
For a full road trip with passengers, drive time and a cost split, use the trip cost calculator. To see what you spend on fuel in a year, try the gas budget calculator.
Want to cut the bill? Read how to save money on gas, see whether premium gas is worth the price, or check what the AC costs you.
Sources
- fueleconomy.gov, Driving more efficiently
- fueleconomy.gov, Maintain your car
- fueleconomy.gov, Download fuel economy data
- AAA gas prices
- EIA gasoline and diesel prices
Last reviewed: October 4, 2026.