Fuel economy can run in either direction
L/100 km describes fuel used over a fixed distance, so a lower number means less fuel under the same conditions. MPG and km/L describe distance covered per fuel volume, so a higher number means less fuel. Comparing the raw numbers without their units can reverse the interpretation.
The fuel cost calculator converts these forms before calculating the trip. It also distinguishes US from UK MPG because a US gallon and an Imperial gallon contain different volumes.
Keep the pump unit independent
A vehicle’s quoted economy might use Imperial MPG while a local pump sells litres. This combination is valid as long as both units are identified and converted. Do not choose US MPG merely because the pump price uses a dollar symbol; currency and measurement system are independent.
For a simple metric check, 500 km at 7.5 L/100 km needs 37.5 L. Multiplying by a price of 1.50 per litre gives 56.25. Changing the displayed units should preserve that physical fuel quantity and cost.
Enter the route convention once
Distance is one-way in this tool. The return option doubles it. If you already entered the entire round trip, leave that option off. Otherwise a return journey can accidentally become four times the true one-way distance.
Constant economy is an estimate, not a route prediction. Congestion, hills, temperature, speed and load can all change observed consumption. Use a measured or plausible scenario and record it with the trip rather than treating a vehicle label as a guarantee.
Split the total without losing cents
Divide the rounded trip total among all contributors you intend to include. For 10.00 and three payers, cent-sized shares are 3.34, 3.33 and 3.33. The small difference is rounding allocation, not an unequal underlying percentage of the trip.
Tolls, parking and other expenses need separate agreement because they are not included here. The unit price calculator compares costs per equal quantity, while the electricity calculator works with energy consumption where that input is applicable.