What is a Fuel Cost Calculator?
The fuel cost calculator computes the cost of driving a given distance from fuel economy and fuel price. It also supports electric vehicle energy cost calculations.
How it's calculated
Fuel cost = distance ÷ fuel economy × fuel price
EV cost = distance ÷ efficiency (km/kWh) × electricity price
Why real-world mileage never matches the sticker
Official fuel economy ratings come from a standardized lab test cycle — conditions that rarely match real driving. Idling in traffic, air conditioning, hard acceleration and braking, and low tire pressure all drag down real-world mileage. A realistic estimate is usually 80–90% of the official rating.
Good to know
- Improving good fuel economy saves less than improving poor fuel economy. Going from 10 to 12 km/L saves far more fuel per 100km than going from 20 to 22 km/L — which is why some countries prefer L/100km, a metric that scales directly with actual savings.
- Above about 100 km/h, fuel economy drops sharply on the highway, because air resistance increases with the square of speed.
- At 5 km/kWh and $0.20/kWh, an EV covers 100km for about $4 — compared to roughly $12–14 for a gasoline car at 12 km/L, fuel cost alone can be 3x or more lower.
- EV charging cost varies a lot by location — home slow charging versus highway fast charging can differ by more than double.
- For long trips, tolls can add up to 30% or more of the fuel cost, so comparing fuel cost alone underestimates total trip expense.
Fuel cost planning reference
| Situation | Note |
|---|---|
| Long highway trips | Tolls can add 30%+ on top of fuel cost |
| Heavy city traffic | Idling drags real-world mileage well below the official rating |
| EV slow charging | Often less than half the cost of fast charging |
| Carpooling | Per-person cost drops proportionally with more riders |
Frequently asked questions
Q. Why does real mileage differ from the official rating?
Official ratings come from standardized test conditions. Real driving includes traffic, AC use, and driving style, which typically lower actual mileage.
Q. How do I convert km/L to L/100km?
Divide 100 by the km/L value. 12 km/L is about 8.3 L/100km.
Q. How is EV efficiency cost calculated?
km/kWh tells you how far you go per kWh. Divide distance by efficiency, then multiply by your electricity rate.