Fuel cost calculator
Distance, economy and fuel price into what the trip costs — with km/L, L/100km and mpg side by side.
Works out what the fuel for a trip costs and what each person owes if you share it. Economy units are converted too: km/L and L/100km are reciprocals, so whether a bigger number is better flips between them — which is where reading an imported spec sheet goes wrong.
The trip
What you enter is saved in this browser, so it is still here next time
Enter it one way
Counts the distance twice.
The average from your trip computer is closest to reality
Per litre
Fuel cost
Fuel cost
₩42,500
Fuel needed
25 L
- Distance driven
- 300 km
- Per km
- ₩142
Per person
₩42,500
- Sharing the cost
- 1
The same economy, three ways
- km/L (Korea)
- 12
- L/100km (Europe)
- 8.33
- mpg (US)
- 28.2
Using the US gallon, 3.785411784 L. An imperial gallon reads about 20% better.
If the economy differs
| Economy | Fuel | Cost |
|---|---|---|
| 6 km/L | 50 L | ₩85,000 |
| 8 km/L | 37.5 L | ₩63,750 |
| 10 km/L | 30 L | ₩51,000 |
| 12 km/L | 25 L | ₩42,500 |
| 14 km/L | 21.4 L | ₩36,429 |
| 16 km/L | 18.8 L | ₩31,875 |
| 18 km/L | 16.7 L | ₩28,333 |
| 20 km/L | 15 L | ₩25,500 |
| 24 km/L | 12.5 L | ₩21,250 |
L/100km is the reciprocal of km/L, so lower is better there. 12 km/L and 8.3 L/100km are the same figure.
Make a link with these numbers
Opening the link fills this screen with the same values. Useful for going through it with a partner, or for comparing two sets of conditions.
Distance ÷ economy × price
For a round trip the one-way distance is doubled first. 150 km each way is 300 km, and at 12 km/L that takes 300 ÷ 12 = 25 L. At 1,700 per litre that is 25 × 1,700 = 42,500. Cost per km is 42,500 ÷ 300 = 141.67 → 142, and the per-person figure divides that by the head count, rounded and never below one. If the economy is zero or below there is nothing to divide by, so the page says so instead of showing a result.
Converting between the three units
L/100km is 100 ÷ (km/L): 12 km/L is 100 ÷ 12 = 8.33 L/100km. mpg is km/L × 3.785411784 ÷ 1.609344, so 12 km/L is 28.2 mpg — one km/L is 2.352 mpg. Going the other way, divide mpg by 2.352: 30 mpg is 12.75 km/L. L/100km back to km/L is again 100 ÷ value, so 6.5 L/100km is 15.4 km/L. This block only re-expresses the value in the economy field; the fuel cost is untouched by it.
The table changes only the economy
The table below recomputes nine rows from 6 to 24 km/L with the same distance and price. The row within 0.25 of your economy is highlighted. For 300 km at 1,700, 10 km/L is 30 L and 51,000; 12 km/L is 25 L and 42,500; 16 km/L is 18.75 L and 31,875. A 20% drop in economy raises the fuel bill by 25% — from 12 to 9.6 km/L is 31.25 L and 53,125. A value in the denominator moves the answer the other way, and by a different amount.
What it does not do
Only fuel is counted. Tolls, parking and depreciation are not. One economy figure covers the whole trip, so motorway and city driving are not separated, and there is no petrol, diesel or LPG setting — enter the price of whatever you use. An electric car's cost per kWh is a different unit and cannot go into this formula. The easiest way to bring the answer close to reality is to enter the average from your trip computer rather than the official figure.
Common questions
QWhy does L/100km read backwards?
km/L asks how far one litre goes; L/100km asks how many litres 100 km takes. Higher is better in the first, lower in the second. 12 km/L is 8.3 L/100km — the same car, the same economy.
QWhich gallon does the mpg use?
The US gallon, 3.785411784 L. The imperial gallon is 4.54609 L, which makes the same car look about 20% better. It is why US and UK figures cannot be compared directly.
QWhy is the real cost higher?
Official economy figures come from a fixed test cycle. Traffic, air conditioning, load and tyre pressure commonly cost 10–20% in practice. Use the average from your own trip computer and the answer gets much closer.
QRoughly what does Seoul to Busan and back cost in fuel?
Take 400 km each way and choose round trip: 800 km. At 12 km/L that is 66.67 L, at 1,700 per litre 113,333, and split four ways 28,333 each. A car doing 16 km/L brings it down to 50 L and 85,000. Tolls are on top.
QHow do I enter an economy given in mpg or L/100km?
Convert to km/L. Divide mpg by 2.352, so 30 mpg is 12.75 km/L; divide 100 by L/100km, so 6.5 L/100km is 15.38 km/L. Imperial mpg uses a bigger gallon and needs dividing by a further 1.2.