Fuel Cost Calculator
Fuel cost for any drive — distance, MPG, and today’s gas price, with round-trip and per-person split.
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People sharing the fuel bill.
You need
$34.29in fuel
10.71 gallons for 300 mi
- Gallons needed
- 10.71 gal
- Distance driven
- 300 mi
In short
How much will gas cost for my trip?
Divide the miles by your MPG, then multiply by the pump price. 300 miles at 28 MPG and $3.20 a gallon burns 10.71 gallons and costs $34.29. Switch on the round trip and it doubles to 600 miles, 21.43 gallons and $68.57. Fuel economy moves the number more than price does: the same 300 miles at 20 MPG costs $48.00.
That is the fuel alone. At the IRS business mileage rate of 76 cents a mile in force from 1 July 2026, the all-in cost of putting 300 miles on your own car is about $228.
How to use the fuel cost calculator
Three numbers decide what a drive costs: how far you are going, how far your car travels on a gallon, and what a gallon costs today. Enter the one-way driving distance from a map app rather than the straight-line distance between two cities, because routes bend around mountains, lakes and interchanges and the difference on a long trip runs to real gallons.
Leave the distance as one way and use the round-trip toggle for the return leg, so you are never doing the doubling in your head at the same time as everything else. With the defaults loaded, 300 miles at 28 MPG and $3.20 a gallon burns 10.71 gallons and costs $34.29; flip round trip and the same drive becomes 600 miles, 21.43 gallons and $68.57.
The arithmetic is trivial, which is exactly why the estimate lives or dies on the quality of the three numbers you feed it.
10.71 gal
The default 300-mile drive
at 28 MPG
$34.29
Fuel bill at $3.20 a gallon
$68.57
As a round trip
600 miles, 21.43 gallons
Fuel economy is where nearly every estimate goes wrong, because the number on the window sticker is a laboratory result and your drive is not a laboratory. The US Department of Energy is blunt about the size of the gap on fueleconomy.gov, condition by condition.
- Aggressive driving, highway speeds
- 15 to 30 percent
- Aggressive driving, stop-and-go traffic
- 10 to 40 percent
- An extra 100 pounds in the vehicle
- about 1 percent
- Roof cargo box, city driving
- 2 to 8 percent
- Roof cargo box, highway
- 6 to 17 percent
- Roof cargo box, interstate speeds
- 10 to 25 percent
- Cold, short 3 to 4 mile winter trips
- up to 24 percent
US Department of Energy figures from fueleconomy.gov. Use your own tracked average if you have one; if you only have the EPA rating, knock it down before you type it.
The split field divides the fuel bill evenly among everyone in the car, which is the simplest fair method for a carpool or a road trip. Bear in mind what it is dividing: fuel, and nothing else. Tolls, parking and the wear on whoever supplied the car are separate conversations, and the gap between those two ideas is large.
The IRS standard business mileage rate, which is meant to stand in for the whole cost of operating a vehicle, rose to 76 cents a mile on 1 July 2026, up from 72.5 cents for the first half of the year. Against the $34.29 of fuel our 300-mile default burns, that same trip is worth about $228 all in.
Use the fuel number when you are comparing a drive against a flight or judging whether a detour is worth it, and the per-mile rate when you want the honest cost of your own car.
Fuel is one line of the trip
Lodging, food and the daily spend sit around it, and they scale with people and days rather than with miles. The budget tool keeps those one-off and per-day costs apart.
Open the trip budget calculator →Do
- Take the driving distance from a map app rather than the straight-line one.
- Enter your own tracked average from the trip computer or a few fill-ups.
- Leave the distance one way and let the round-trip toggle double it.
- Shade the EPA rating down before typing it, if it is all you have.
Don't
- Type a litres per 100 km figure into the MPG field.
- Pair a per-litre price with a per-gallon economy, or convert only one side.
- Read a quoted imperial mpg as though it were the US figure.
- Settle a carpool on fuel alone when tolls, parking and wear sit outside it.
What your fuel economy is worth, in both unit systems and in dollars. Every row is the same car described four ways: the US MPG figure, the litres per 100 kilometres a European spec sheet would quote, the kilometres per litre used across much of Asia and Latin America, and what the tool’s default 300-mile drive actually costs at that efficiency. Reading across a row is the fastest way to catch a unit mistake before it becomes a budget mistake.
| Fuel economy (US MPG) | Same car in L/100 km | Same car in km per litre | Gallons for a 300-mile drive | Fuel cost at $3.20 a gallon |
|---|---|---|---|---|
| 15 MPG (large SUV or pickup, towing) | 15.68 L/100 km | 6.38 km/L | 20.00 gal | $64.00 |
| 18 MPG (full-size SUV, city driving) | 13.07 L/100 km | 7.65 km/L | 16.67 gal | $53.33 |
| 20 MPG (older V6 sedan) | 11.76 L/100 km | 8.50 km/L | 15.00 gal | $48.00 |
| 22 MPG (mid-size crossover) | 10.69 L/100 km | 9.35 km/L | 13.64 gal | $43.64 |
| 25 MPG (compact crossover) | 9.41 L/100 km | 10.63 km/L | 12.00 gal | $38.40 |
| 28 MPG (the calculator default) | 8.40 L/100 km | 11.90 km/L | 10.71 gal | $34.29 |
| 30 MPG (compact sedan) | 7.84 L/100 km | 12.75 km/L | 10.00 gal | $32.00 |
| 32 MPG (small turbo sedan) | 7.35 L/100 km | 13.61 km/L | 9.38 gal | $30.00 |
| 35 MPG (efficient compact) | 6.72 L/100 km | 14.88 km/L | 8.57 gal | $27.43 |
| 40 MPG (mild hybrid or diesel) | 5.88 L/100 km | 17.01 km/L | 7.50 gal | $24.00 |
| 45 MPG (full hybrid, mixed driving) | 5.23 L/100 km | 19.13 km/L | 6.67 gal | $21.33 |
| 50 MPG (full hybrid, steady highway) | 4.70 L/100 km | 21.26 km/L | 6.00 gal | $19.20 |
| 55 MPG (best-case hybrid) | 4.28 L/100 km | 23.38 km/L | 5.45 gal | $17.45 |
| 60 MPG (plug-in running on fuel) | 3.92 L/100 km | 25.51 km/L | 5.00 gal | $16.00 |
Why fuel economy outweighs the pump price
Run the same drive at two other efficiencies, so you can see the leverage. A 20 MPG vehicle needs 300 / 20 = 15.00 gallons and pays $48.00, which is $13.71 more than the default. A 40 MPG vehicle needs 7.50 gallons and pays $24.00, which is $10.29 less.
The spread between those two cars on one 300-mile drive is $24.00, and it is exactly double across a round trip. Now compare that against price: taking the same 28 MPG car from $3.20 to $3.60 a gallon, a swing of 40 cents, moves the bill from $34.29 to $38.57, a difference of $4.28.
Read it: Fuel economy sits in a denominator, so doubling MPG halves the bill, while a 40-cent price swing moves the same drive by $4.28.
Computed from gallons = miles ÷ MPG, then gallons × price.
Full guide
How Much Will Gas Cost for My Trip? Road-Trip Fuel Math
Three numbers set the fuel bill: miles driven, the MPG you actually get, and today's price. Most bad estimates get the middle one wrong.
Read the full guide →The formula, worked line by line
The whole calculation is a division followed by a multiplication, with an optional doubling in front and an optional division at the end. Distance divided by fuel economy gives gallons, and gallons multiplied by the pump price gives dollars. The round-trip toggle doubles the distance before anything else happens, and the traveller count divides the money after everything else has happened, so neither one changes the shape of the middle.
It is worth seeing why fuel economy is the dominant term. Price appears once, as a straight multiplier, so a 10 percent rise in the pump price raises the bill by 10 percent. Fuel economy appears in a denominator, so it works on the gallons before the price ever touches them.
Doubling MPG halves the cost, because it halves the gallons first, which is why the difference between a 20 MPG vehicle and a 40 MPG vehicle on the same route is larger than almost any price swing you will live through.
distance driven = distance x (round trip ? 2 : 1)
gallons = distance driven / MPG
cost = gallons x price per gallon
per person = cost / travelers- Distance
- 300 miles, one way
- Gallons
- 300 / 28 = 10.714
- Fuel cost
- 10.714 x $3.20
- Trip fuel bill
- $34.29
Turn on the round trip and the distance becomes 600 miles, the fuel becomes 21.429 gallons, and the bill becomes $68.57. Split that round trip between two people and each owes $34.29, the neat coincidence that the return leg costs the same as the one-way trip did alone.
Two conversions worth keeping nearby if your inputs came from outside the United States. To move between the two economy scales, divide 235.2146 by either figure to get the other: 235.2146 / 28 MPG = 8.40 L/100 km, and 235.2146 / 8.40 = 28 MPG.
To move a per-litre price into a per-gallon price, multiply by 3.785411784. A pump reading 1.80 a litre is 6.81 a gallon in the same currency, and the 300-mile default at 28 MPG would then cost 73.00 rather than $34.29. Convert both the economy and the price, or convert neither, and never one without the other.
Questions people ask
Sources
Where the constants and formulas on this page come from. Each line names the figure it backs.
The standard business mileage rate of 76 cents a mile from 1 July 2026, up from 72.5 cents for the first half of the year.
Standard mileage rates — US Internal Revenue Service, 76 cents per mile, 1 July to 31 December 2026
The driving penalties in the conditions ledger: 15 to 30 percent for aggressive highway driving, 10 to 40 percent stop-and-go, about 1 percent per extra 100 pounds, and 2 to 25 percent for a roof cargo box.
Gas Mileage Tips — Driving More Efficiently — US Department of Energy and US EPA (fueleconomy.gov)
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