Gas Cost Calculator
＋More features: split the cost, commuting fuel cost
Split it between everyone (tolls included)
Enter the number of people and the toll charges to get the amount per person (distance, fuel economy and price come from the form above).
Commuting fuel cost (per month and per year)
From your one-way distance and the number of days you go in, this works out the fuel cost per month and per year (fuel economy and price come from the form above).
Enter the distance you will drive and your car’s fuel economy, and you see how much the petrol will cost. You can also split the total per person with tolls added, or work out what commuting costs you each month. Amounts are in Japanese yen and fuel economy is in km/L, the way it is quoted in Japan. Handy for budgeting a trip or a visit home.
How to use
- Enter the distance you will drive (or drove) in kilometres. The distance from a route search in a map app works well.
- Enter your car’s fuel economy (km/L). If you know your real-world figure, use that.
- Enter the petrol price (yen/L) and the amount appears automatically just below.
How it is calculated
- Fuel used (L) = distance (km) ÷ fuel economy (km/L)
- Fuel cost (yen) = fuel used (L) × price per litre (yen/L)
- Example: 100 km at 15 km/L with petrol at 170 yen/L → 6.67 L, about 1,133 yen
Sources and assumptions
- The above is arithmetic derived from the definitions of distance, fuel economy and unit price (fuel is rounded to two decimal places, amounts to the nearest yen).
- Catalogue fuel economy (WLTC mode and similar) is measured under fixed conditions and differs from real-world figures. For a round trip, double the distance before calculating.
Assumptions and notes
- Expressway tolls and parking charges are not included in the main calculation.
- Fuel economy varies widely between hybrids, kei cars and so on, so accuracy improves if you work out your real-world figure from your own refuelling records (distance driven ÷ litres filled).
Frequently asked questions
How do I find my car’s real-world fuel economy?
The full-tank method is easiest. Fill the tank, drive, then divide the distance driven by the litres it takes to fill the tank again — that gives your real-world figure in km/L.
How do I calculate a round trip?
Double the distance (for a 100 km one-way trip, enter 200 km).
Does the catalogue figure make the cost look too cheap?
Real-world fuel economy is generally worse than the catalogue value (WLTC mode and similar). To leave a margin, enter roughly 70–80% of the catalogue figure and the result will be closer to reality.