People type this into search every day: road trip fuel cost calculator.
The usual answer is “miles divided by MPG, times the pump price.” That is the right idea. It still needs three numbers you can measure: the full route, how much fuel the car uses, and what you will pay at the pump.
I am not going to invent a national average for what a weekend trip costs. Fuel prices move every week. The US Energy Information Administration publishes a Monday pump-price survey. Use that page, or the sticker on the station you will actually stop at.
The formula is litres, then dollars
The road trip fuel cost calculator uses:
distance ÷ 100 × consumption × fuel price
Distance is the whole route. The field is labeled round-trip distance. If you type the one-way figure, you price half the drive.
Consumption is litres per 100 kilometres. The tool assumes that rate stays constant across the route. Tolls and parking sit outside this estimate.
Here are the published defaults:
- round-trip distance: 850 km
- vehicle consumption: 7.4 L / 100 km
- fuel price: $1.78 / L
- travelers splitting cost: 2
Fuel needed: 850 ÷ 100 × 7.4 = 62.9 L
Total fuel cost: 62.9 × 1.78 = $111.96
Per traveler: 111.96 ÷ 2 = $55.98
Calculator result
Road trip fuel cost
- Round-trip distance
- 850 km
- Vehicle consumption
- 7.4 L / 100 km
- Fuel price
- $1.78
- Travelers splitting cost
- 2 people
$111.96
total fuel cost
- Fuel needed
- 16.6 gal
- Per traveler
- $55.98
- Cost / 100 mi
- $21.20
On a US display those 62.9 L show as 16.6 gal. Cost per 100 km converts to $21.20 / 100 mi.
850 km is 528.2 mi. That is a labeled example. Your route will differ.
Fig 1 · 1/2
Two people, one tank
850 km, 7.4 L/100 km, $1.78/L
You
$55.98
The other person
$55.98
The tank costs $111.96 for the full route.
Split two ways, each traveler pays $55.98.
Get consumption from your own tank, not a brochure
The sticker on the window is a laboratory comparison. EPA’s calculating your MPG page uses the tank you actually fill.
Their odometer example: 33,001.3 minus 32,645.1 is 356.2 miles. It took 13.5 gallons to fill. 356.2 ÷ 13.5 = 26.4 MPG.
Their trip-odometer example: 335 miles on 9.5 gallons. 335 ÷ 9.5 = 35.5 MPG.
Those are EPA’s examples. They are not this calculator’s defaults.
Once you have MPG, convert it before you type litres per 100 km. The fuel economy converter uses:
US MPG = 235.215 ÷ L/100 km
Default 7.4 L/100 km prints 31.8 MPG. Imperial MPG: 38.2. Kilometres per litre: 13.51.
EPA’s driving more efficiently page also writes cost per 100 miles as fuel price ÷ MPG × 100. That is the same rate the road-trip tool prints after unit conversion. At 7.4 L/100 km and $1.78/L, that rate is $21.20 / 100 mi.
Forgetting the return trip halves the bill
The field says round-trip. Type 425 km on the same car and the same $1.78:
Fuel: 425 ÷ 100 × 7.4 = 31.45 L
Cost: $55.98
Per traveler: $27.99
That $55.98 is half of $111.96. You did not find cheaper fuel. You priced one direction.
Double the default to 1,700 km. Cost: $223.92. Per traveler: $111.96, which is the whole default trip paid by one person.
Fig 2 · 1/1
Fuel cost as the route grows
7.4 L/100 km and $1.78/L. Distance is the only change.
Total fuel cost
- Fuel cost
| Point | Fuel cost |
|---|---|
| 425 km | $56 |
| 850 km | $112 |
| 1,200 km | $158 |
| 1,700 km | $224 |
A 425 km one-way figure prints $55.98.
The 850 km default is $111.96. 1,700 km is $223.92.
I would put both directions in that box, including the airport loop or the grocery stop on the way home. The formula does not invent extra miles.
Sharing the tank does not change the litres
Two people is the default. The litres stay 62.9. Only the share moves.
Three people: 111.96 ÷ 3 = $37.32
Four people: 111.96 ÷ 4 = $27.99
One person: $111.96
Fig 3 · 1/1
Same $111.96, more seats
850 km default route. Only the people field changes.
- Share
| Category | Share |
|---|---|
| 1 person | $112 |
| 2 people | $56 |
| 3 people | $37 |
| 4 people | $28 |
One driver pays the full $111.96.
Two people pay $55.98 each. Four people pay $27.99.
If you paid the station, the group trip expense split does the same division after the fact. Shared total $111.96, two travelers, you paid $111.96: each share is $55.98, and you should receive $55.98. That matches the fuel tool.
The roommate post on splitting rent uses the same equal-share idea. Fuel is easier. There is no larger bedroom.
Consumption is the lever you feel on a long drive
EPA says aggressive driving (speeding, rapid acceleration and braking) can lower highway gas mileage by roughly 15% to 30%. That sentence is on the driving more efficiently page. It is a range from their cited studies, not a promise for your car.
The default 7.4 L/100 km is 31.8 MPG. A 15% drop in that MPG is about 27.0 MPG, which is 8.7 L/100 km. A 30% drop is about 22.2 MPG, which is 10.6 L/100 km.
Keep 850 km, $1.78/L, and two people. Change only consumption:
- 5.5 L/100 km (42.8 MPG): $83.22, $41.61 each
- 7.4 L/100 km (default): $111.96, $55.98 each
- 8.7 L/100 km (about 15% less MPG): $131.63, $65.82 each
- 9.5 L/100 km (24.8 MPG): $143.74, $71.87 each
- 10.6 L/100 km (about 30% less MPG): $160.38, $80.19 each
Fig 4 · 1/3
Same 850 km, five consumption rates
$1.78/L. Two travelers. Only litres per 100 km change.
Total fuel cost
5.5 L/100 km
$83.22
7.4 L/100 km
$111.96
10.6 L/100 km
$160.38
At 5.5 L/100 km the trip is $83.22.
The 7.4 default is $111.96.
At 10.6 L/100 km, near a 30% MPG drop, the trip is $160.38.
The $48.42 gap between $83.22 and $131.63 is still the same 850 km. You changed how thirsty the car is.
EPA also notes that each extra 100 pounds can cut MPG by about 1%, and that a large roof box can cut highway fuel economy by 6% to 17%. Those are their published ranges. Put the consumption you measure with the loaded car into the box. Do not add a second fudge factor on top of a tank reading you already took.
The price you type should be this week’s pump
EIA’s Gasoline and Diesel Fuel Update for the week of 12 October 2026 lists US regular at $4.331 / gal. That is their survey, not a forecast.
$4.331 per US gallon is $1.144 / L. Put 1.144 in the price field. Keep 850 km, 7.4 L/100 km, and two people.
Cost: $71.96
Per traveler: $35.98
Cost / 100 mi: $13.62
The litres are still 62.9. Only the price changed.
Raise the default $1.78 to $2.10 and keep everything else:
Cost: $132.09
Per traveler: $66.05
Fig 5 · 1/1
Three pump prices, one route
850 km at 7.4 L/100 km. Two travelers.
- Fuel cost
| Category | Fuel cost |
|---|---|
| $1.144/L | $72 |
| $1.78/L | $112 |
| $2.10/L | $132 |
EIA week-of-12-October $4.331/gal ($1.144/L) prints $71.96.
The calculator default $1.78/L prints $111.96. $2.10/L prints $132.09.
EPA’s 2026 Fuel Economy Guide prices annual fuel cost with 15,000 miles and $4.33 / gal for regular, then rounds to the nearest $50. That is a window-sticker method. It is not this trip calculator. For one route, type the kilometres and the price you will pay.
If prices change along the drive, EIA’s own note is that the weekly figure is a Monday survey. Use a weighted average, or run the calculator once per fill.
An 800 km editorial example
The calculator page walks an 800 km trip at 7.2 L/100 km and $1.75/L, split two ways.
Fuel: 800 ÷ 100 × 7.2 = 57.6 L
Cost: 57.6 × 1.75 = $100.80
Per traveler: $50.40
7.2 L/100 km is 32.7 MPG.
Calculator result
Road trip fuel cost
- Round-trip distance
- 800 km
- Vehicle consumption
- 7.2 L / 100 km
- Fuel price
- $1.75
- Travelers splitting cost
- 2 people
$100.80
total fuel cost
- Fuel needed
- 15.2 gal
- Per traveler
- $50.40
- Cost / 100 mi
- $20.28
That $100.80 is useful next to a train fare. It is still only fuel.
The same 850 km in an electric car
The EV road trip charging cost calculator uses the same 850 km default. It multiplies distance by kWh per 100 km, adds charging loss, then blends two electricity prices.
Defaults:
- trip distance: 850 km
- vehicle efficiency: 18 kWh / 100 km
- fast-charging share: 70%
- fast-charging price: $0.58 / kWh
- other charging price: $0.25 / kWh
- charging loss: 10%
Grid energy: 850 ÷ 100 × 18 × 1.10 = 168.3 kWh
Blended rate: 0.70 × 0.58 + 0.30 × 0.25 = $0.481 / kWh
Trip charging cost: 168.3 × 0.481 = $80.95
Calculator result
EV road trip charging cost
- Trip distance
- 850 km
- Vehicle efficiency
- 18 kWh / 100 km
- Fast-charging share
- 70%
- Fast-charging price
- $0.58
- Other charging price
- $0.25
- Charging loss
- 10%
$80.95
trip charging cost
- Grid energy
- 168.3 kWh
- Blended rate
- $0.48
- Cost / 100 mi
- $15.33
All fast charging: $97.61. All other charging: $42.08. Parking and session fees are excluded, same as tolls on the fuel tool.
Fig 6 · 1/3
850 km, fuel or electrons
Fuel defaults vs EV defaults. Same distance.
Energy cost
Petrol default
$111.96
EV blended
$80.95
EV all-fast
$97.61
The petrol default is $111.96.
The EV default blend is $80.95. All-fast charging is $97.61.
$80.95 versus $111.96 is this pair of defaults. It is not a national EV-versus-petrol statistic.
Fuel is one line on a trip budget
The tool’s assumptions say tolls and parking are excluded. So is depreciation. The commute cost calculator prices a work week with a vehicle operating cost per kilometre plus daily parking. Its default year is $4,884.48. That is a different question from one 850 km weekend.
If you are choosing car versus train versus flight, the car vs train vs flight calculator wants a car total that already includes fuel, tolls, parking, and wear. Do not drop $111.96 in as the whole car cost unless that is really all you will spend.
Subscriptions on the yearly stack are leftover-cash questions. $55.98 does not decide them. The salary to hourly post converts a paycheck. It does not price a tank.
This is a fuel estimate. It is not a travel budget, and it is not advice about whether you should drive. Open the road trip fuel cost calculator with the kilometres you will actually cover, the consumption you measured on a similar road, and the price on the pump you will use. If a second person is coming, leave the people field at 2 and split $55.98 after you fill.