Fuel Cost & Mileage Calculator

How to use

1. Enter the distance to where you are going in "Distance (one way)". Press "Round trip" to double it. The distance from a route search in a map app goes in as it is.
2. Enter the car's fuel economy in "Fuel economy". Choose its unit: km/L (how far a litre takes you) or L/100km (how many litres 100 km takes). The economy you measure yourself by the fill-up method gives a closer figure than the WLTC figure in the catalog.
3. Change "Fuel price (yen/L)" to the price at your station. It starts at 170.1 yen/L, Japan's national average for regular on 13 October 2026.
4. To share tolls or parking as well, enter their total for the whole drive in "Tolls, parking and so on".
5. With two or more people, enter "People in the car" to see the amount per person in large type. "Leave the driver out of the split" then appears; tick it if the driver does not pay. Each share is rounded up to 1, 10, or 100 yen, as you choose.

The result lists the distance driven, the fuel used in litres, the fuel cost and the fuel cost per km, the total with tolls, and what is collected against the total. "Copy result" copies the conditions and amounts as text. The quick table under the result gives the fuel cost for one-way distances from 10 to 500 km and several economies, at the price you entered.

Switch to "Mileage (fill-up method)" to work out the fuel economy from your fill-ups. Enter the distance driven from filling the tank to filling it again and the fuel put in the second time to see km/L and L/100km. Add the amount paid to see the price per litre and the fuel cost per km too. "Work out a fuel cost with this economy" puts that economy into the fuel cost calculation and switches to it. It goes in the unit chosen there, so with L/100km chosen the L/100km figure goes in. When the figure is outside what that field takes (0.01 to 100), a note shows instead of the button.

How it is calculated

• Fuel used (L) = distance driven (km) ÷ economy (km/L)
• With the economy in L/100km: fuel used (L) = distance driven (km) × economy (L/100km) ÷ 100
• Fuel cost = fuel used × fuel price
• Total = fuel cost + tolls, parking and so on
• Per person = total ÷ the people sharing it, rounded up to the unit chosen
• Mileage by the fill-up method (km/L) = distance driven ÷ fuel put in the second time

The working is exact and rounded only once at the end. Fuel is rounded half up to 0.01 L and the fuel cost to the nearest yen, and the total is the rounded fuel cost plus the other costs. Each share is rounded up so that what is collected never falls short of the total, so the amount collected can come to a little more than the total; the difference is shown as "over". Economy figures are rounded to 0.01, and the price per litre and the cost per km to 0.1 yen.

Full-width digits and thousands separators such as 1,200 are read too.

Example

A round trip of 150 km each way, an economy of 15 km/L, fuel at 170.1 yen/L, 6,000 yen of tolls for the whole drive, and four people splitting it without the driver, rounded up to 10 yen:

Distance driven   300 km (150 km each way)
Fuel used         about 20.00 L
Fuel cost         3,402 yen (11.3 yen per km)
Tolls and so on   6,000 yen
Total             9,402 yen
Per person        3,140 yen (Split among the 3 besides the driver · 9,420 yen collected, 18 yen over)

A fill-up example: after 520 km since the last full tank, 34.5 L costing 5,900 yen fills it again. That is 15.07 km/L (6.63 L/100km), 171.0 yen per litre, and 11.3 yen per km.

Notes

• Real fuel economy changes with traffic, hills, luggage, air conditioning, and motorway speeds. A catalog economy usually gives a lower cost than you will pay, so budget a little more.
• Fuel prices differ by region and by week. The starting 170.1 yen/L is the national average on 13 October 2026 in the petroleum product price survey for the Agency for Natural Resources and Energy.
• For a diesel car or premium petrol, enter that price and the same formulas apply.
• What you enter is worked out in your browser only. Nothing is sent or saved.

FAQ

Where do I find the fuel economy?

Catalogs and the vehicle inspection certificate give the WLTC economy in km/L. The average shown on the dashboard, or a figure measured with "Mileage (fill-up method)" here, is closer to how you actually drive. For a figure in L/100km, as with many imported cars and figures from abroad, switch the unit to "L/100km" and enter it as it is.

What is the fill-up method?

Fill the tank, reset the trip meter, and the next time you fill the tank, divide the distance on the meter by the fuel it took. Filling until the pump stops by itself both times keeps the error small. Adding up several fill-ups and dividing the total distance by the total fuel gives a figure closer to your average.

Should the driver pay a share of the fuel?

There is no rule. Some groups split it evenly, some leave the driver out, and some thank the driver with a meal instead. To leave the driver out, tick "Leave the driver out of the split".

Why do the shares not add up to the total?

Each share is rounded up so that what is collected covers the total. Splitting 9,402 yen four ways gives 2,350.5 yen; rounded up to 10 yen that is 2,360 yen, so 9,440 yen is collected, 38 yen over. Even a total that divides evenly can come out over with 10 or 100 yen chosen: 9,402 yen three ways is exactly 3,134 yen, but 3,140 yen when rounded up to 10 yen, 18 yen over. Decide among yourselves what to do with the extra, such as giving it to the driver.

Can it work out the charging cost of an electric car?

Enter the efficiency in km/kWh as the economy and the electricity rate in yen/kWh as the price, and the same formulas give the electricity cost. The units still say litres, so read them as kWh. For the electricity cost of home appliances, use the Electricity Cost Calculator.