Fuel Cost Calculator

Estimate trip costs, split budgets with co-passengers, compare vehicle efficiencies, and measure mileage.

Trip Parameters

Distance

Fuel Efficiency

Fuel Price

Number of Trips

Co-Passengers (Splitter)

Trip Costs

Total Cost:$36.00

Total Fuel Needed:24.00 L

Commute Cost Projections

Daily (Round Trip):$72.00

Weekly Commute:$360.00

Monthly Commute:$1584.00

Yearly Commute:$17280.00

How fuel costs and efficiencies are calculated

Fuel consumption is calculated by converting the trip distance to kilometers and vehicle efficiency to Liters per 100 Kilometers (L/100km). The total fuel required in liters is: Liters = (Distance in km × L/100km) / 100. Multiplying this by the fuel price (converted to cost per liter) yields the total trip cost.

Passenger splits divide total trip costs evenly. Commute cost projections extrapolate daily round trips across standard 5-day workweeks, monthly cycles, and annual working schedules.

Built and maintained by Meet Shah · Last updated 1 August 2026

What this tool is used for

Estimating the fuel cost of a trip before setting off.
Comparing two routes on fuel cost rather than distance.
Working out cost per mile or kilometre for an expense claim.
Comparing two vehicles on the same journey.
Estimating a monthly commuting cost from a daily round trip.

Frequently Asked Questions

How does it convert between mpg and L/100km?: By division, not multiplication, because the two units run in opposite directions — more mpg is better, more L/100km is worse. US mpg uses 235.215 ÷ mpg, imperial mpg uses 282.481 ÷ mpg. The constants differ because the imperial gallon (4.54609 L) is about 20% larger than the US gallon (3.78541 L).
Why is 30 mpg US not the same as 30 mpg UK?: Because the gallons are different volumes. 30 mpg US is 7.84 L/100km; 30 mpg imperial is 9.42 L/100km — a 20% gap that comes entirely from the unit. UK car reviews quoting mpg are almost always imperial, so comparing them directly with a US EPA figure overstates the British car's economy.
What do the commute projections assume?: Two trips a day (there and back), five days a week, 22 days a month and 240 days a year. Those are working-pattern assumptions, not measurements — if you commute four days a week or take six weeks of leave, scale the yearly figure down accordingly. The per-trip cost underneath them is exact.
What annual mileage does the vehicle comparison use?: 15,000 km. The comparison computes the cost difference per 100 km and multiplies by 150, so if your yearly distance is different, the annual saving scales linearly — 30,000 km doubles it. The per-100km difference shown alongside it is the figure that carries over to any mileage.
Does splitting the cost between passengers change the fuel used?: No. Fuel consumption is a property of the car and the distance; the passenger count only divides the total bill. It is there for carpool settlement, and it is also the honest argument for sharing a ride — four people in one car pay a quarter each of a cost that four separate cars would have incurred four times over.

Common errors and gotchas

Using a manufacturer's economy figure, which real driving rarely matches.
Mixing units — litres with miles, or gallons with kilometres — without converting.
Confusing US and imperial gallons, which differ by about 20%.
Ignoring that economy varies substantially with speed, load and traffic.
Using a stale fuel price, which moves week to week.