How to Estimate a Fuel Cost
By Tools Star Hub Editorial Team · Published · Updated
Fuel cost is the fuel you use times the price. In miles-per-gallon mode, fuel is distance divided by economy. 120 miles at 30 mpg uses 4 gallons. At $3.50 a gallon, one trip costs $14. In liters-per-100-km mode, fuel is distance times the economy divided by 100. 100 km at 8 L/100 km uses 8 liters. At $1.50 a liter, one trip costs $12, and four of those trips cost $48.
A long drive is easier to budget when the gallons or liters are visible, not just the ticket price. The same distance costs a different amount when the car’s economy or the price changes. This estimate uses the numbers you type. It does not look up a route, a live fuel price, or the car’s actual consumption.
How does the miles-per-gallon estimate work?
Divide distance by miles per gallon to get gallons for one trip. Multiply by the price to get the cost of that trip. Multiply by the number of trips for the total. 120 divided by 30 is 4 gallons. 4 times 3.50 is 14 dollars. One trip and four trips are different totals, so type the trip count you mean.
Miles per gallon must be greater than 0. The page rejects 0 because it cannot divide by it. Distance and price cannot be negative. The result rounds fuel to four decimal places and money to cents.
How does liters per 100 km work?
Liters per 100 km already means fuel for a fixed distance. Multiply the distance in kilometers by that figure divided by 100. 100 km at 8 L/100 km is 8 liters. 8 times $1.50 is $12 for one trip. Four trips use 32 liters and cost $48.
Do not put miles into the kilometer mode, or kilometers into the miles mode. The page does not convert the distance for you. Use the unit converter first if the odometer and the economy figure are in different systems. The economy in this mode must be 1,000 L/100 km or less.
What does this estimate leave out?
Trips must be a whole number from 1 to 100,000. A fraction is rejected. The page does not add tolls, parking, or a round trip unless you include that distance yourself. A return journey is a larger distance or a second trip, and those are not the same if the route differs.
Real cars use more fuel in traffic, in the cold, or with a heavy load. Type the economy you want to assume. The calculator will not replace it with a rated figure, because it does not know the vehicle.
How to estimate a fuel cost
- Choose miles per gallon or liters per 100 km. Match the mode to the economy figure you have. The distance unit has to match that mode.
- Enter distance, economy, and price. Price is per gallon in the miles mode and per liter in the kilometer mode.
- Enter a whole number of trips. Use 1 for a single drive. The total multiplies the one-trip fuel and cost by that count.
- Read fuel and cost. The page shows fuel and cost for one trip and for all trips. Money is rounded to cents.
Example
120 miles at 30 mpg
At $3.50 a gallon and 1 trip, the result is 4 gallons and $14. Both the one-trip figures and the totals match, because there is only one trip.
100 km at 8 L/100 km, four times
At $1.50 a liter, one trip is 8 liters and $12. Four trips are 32 liters and $48.
Common mistakes
The modes do not convert distance
120 miles is not 120 kilometers. Switch modes only when both the distance and the economy figure belong to that mode.
A round trip is extra distance
Typing the one-way distance and 1 trip prices one way. Double the distance or set trips to 2 if both directions are the same length.
FAQ
- How much fuel is 120 miles at 30 mpg?
- 4 gallons. At $3.50 a gallon and 1 trip, the cost is $14.
- How is liters per 100 km calculated?
- Fuel equals distance times the economy divided by 100. 100 km at 8 L/100 km is 8 liters, which is $12 at $1.50 a liter.
- Can I enter half a trip?
- No. Trips must be a whole number from 1 to 100,000.
- Does the page include tolls?
- No. It multiplies fuel by the price you type. Add tolls or parking yourself if you need them.
- Is a route looked up?
- No. The estimate uses the distance, economy, price, and trip count you enter. It runs in the browser.
To price a drive from distance, economy, and fuel price, use the Fuel Cost Calculator. It supports miles per gallon and liters per 100 km.
If the distance is in the wrong system, read How to convert length, weight, and temperature.
Fuel price math is ordinary percent and multiplication. See How to calculate a percentage.