Total fuel cost for a trip, from distance, fuel efficiency and fuel price.
Distance is in kilometers, fuel efficiency is in km per liter, and fuel price is per liter — if your car's efficiency is quoted in a different unit (like MPG), convert it to km/liter first for an accurate cost.
It's your total trip cost scaled to a standard 100 km distance, which makes it easy to compare fuel cost per distance across trips of different lengths or against another vehicle's figures.
Yes — the round-trip figure assumes the return leg covers the same distance at the same efficiency and price, so it's simply the one-way fuel cost multiplied by two.