# How to Compute Fuel Cost

The amount you spend every day, week, or month on gasoline depends on how much you drive, your car's fuel efficiency, and of course, the price of gas. If you know these three variables, you can figure your gas costs on a daily, weekly, or monthly basis. The equation and some examples are explained below, but you can also use the calculator on the left.

### Fuel Cost Formula

Let D be the number of miles you drive per fixed unit of time, let E be your car's fuel efficiency in miles per gallon, and let P be the price of gasoline per gallon. The amount of money you spend per unit of time is given by the equationCost = DP/E.

Example: Suppose you drive 155 miles during a typical week and your car's fuel economy is 31 mpg. If the current price of gas is $5 per gallon, then your weekly gas cost is

(155)(5)/31 = $25.

The same formula can be used for metric measurements, i.e., if you measure distance in kilometers and efficiency in km per liter, and buy gas by the liter. For instance, if you drive 1040 km per month, your vehicle gets 13 km/L (KPL or KMPL), and gas costs $1.25 per liter, then your monthly gas costs are

(1040)(1.25)/13 = $100.

### Alternative Fuel Cost Formula

In some countries, fuel consumption rather than fuel efficiency is used. The units of fuel consumption are liters per 100 kilometers, abbreviated L/100km. If C is the fuel consumption, then the cost of gas is given by the formulaCost = DPC/100.

Example: Suppose your car uses 8 liters of fuel per 100 kilometers. If you drive 2215 km per month and gas costs $1.30 per liter then you pay

(2215)(1.30)(8)/100 = $230.36 per month.

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