About

Planning a road trip or organizing a carpool involves more than just guessing gas money. Fuel efficiency is a dynamic variable affected by aerodynamics and weight. Adding a roof box or a trailer can degrade fuel economy by 10% to 15% due to drag. This tool provides a precise financial breakdown for drivers and passengers.

It features a robust converter for the non-linear relationship between Imperial MPG and Metric L/100km (x L/100km ≈ 235.21 / y MPG). The "Break-even" widget is designed for shared rides, calculating the exact contribution per passenger to ensure fairness.

Formulas

We normalize all inputs to Metric before calculating cost, then convert back if necessary.

If MPG: L/100km = 235.21MPG

Fuel = Dist100 × Consumption × LoadFactor

Load Factor is 1.15 (15% penalty) if extra load is detected. Cost is simply Fuel multiplied by Price.

Reference Data

Efficiency (MPG)	Efficiency (L/100km)	Cost per 100km ($1.50/L)
15 MPG (Truck)	15.7 L/100km	$23.55
25 MPG (Sedan)	9.4 L/100km	$14.10
40 MPG (Hybrid)	5.9 L/100km	$8.85
50 MPG (EV/Diesel)	4.7 L/100km	$7.05

Frequently Asked Questions

Yes, significantly. Even an empty roof rack increases aerodynamic drag. A loaded roof box can increase fuel consumption by 10% to 25% at highway speeds (70mph+) because the engine must work harder to push against air resistance.

Simply double your "Trip Distance" input. Alternatively, calculate the one-way cost and multiply the final dollar amount by 2.

Miles Per Gallon measures distance per unit of volume, while Liters per 100km measures volume per unit of distance. They are inverse reciprocals. Improving from 10 to 20 MPG saves much more fuel than improving from 50 to 60 MPG.