Gas for a trip: what it costs, and how far the money goes

How the page counts

• The miles in all: the miles one way, times 2 for there and back, times how many times.
• The gallons: the miles in all, divided by the miles the car goes on one gallon. The page shows them to the nearest hundredth.
• The cost: the gallons, times the price of one gallon, to the nearest cent. The page keeps the whole division until the end, so rounding the gallons does not move the cost.
• A price can have three places, like 3.459, the way a pump prints it.
• How far money goes: the money, divided by the price of one gallon, times the miles the car goes on one gallon. Only whole miles are counted, and a part of a mile is left off.
• Miles a gallon: the miles driven since the last fill-up, divided by the gallons it took to fill the tank again, to the nearest tenth.
• The page only multiplies and divides. It uses the numbers you type and nothing else.

Examples, worked by hand.

• 15 miles one way, there and back, in a car that goes 30 miles on one gallon, with gas at $3.60: 15 × 2 = 30 miles. 30 ÷ 30 = 1 gallon. 1 × $3.60 = $3.60. Five times: 15 × 2 × 5 = 150 miles, 150 ÷ 30 = 5 gallons, and 5 × $3.60 = $18.00.
• 42 miles, one way only, at 25 miles a gallon, with gas at $3.459: 42 ÷ 25 = 1.68 gallons. 1.68 × $3.459 is about $5.81.
• 100 miles one way, there and back, at 27 miles a gallon, with gas at $3.60: 100 × 2 = 200 miles. 200 ÷ 27 is about 7.41 gallons, and the cost is about $26.67.
• $20 for gas at $3.60, at 27 miles a gallon: $20 ÷ $3.60 is a little more than 5.55 gallons. That is enough for 150 whole miles, or 75 whole miles each way.
• 310 miles on 10.5 gallons: 310 ÷ 10.5 is about 29.5 miles a gallon.

The examples are made up. A program checks them, and 400 made-up counts done a second way, every time the page is built.

Where these counts trip people up

• There and back is twice the miles. A place 15 miles away is 30 miles of driving.
• Miles a gallon divides. 150 miles at 30 miles a gallon is 150 ÷ 30 = 5 gallons.
• Rounding before the end moves the answer. 200 miles at 27 miles a gallon is about 7.41 gallons. 7.41 × $3.60 comes to $26.68, but the whole division comes to $26.67.
• The 9 at the end of the price counts. 10 gallons at $3.459 is $34.59. At $3.45 it would be $34.50.
• Each way is half. Money that is enough for 150 miles is enough for a place 75 miles away, if you are coming back.
• A fill-up count needs a full tank both times. If the tank was not full at the start, the gallons at the second fill do not match the miles.

What this page does not know

• It does not know your car. The miles it goes on one gallon is a number you type, and real driving differs from one day to the next.
• It does not know the price at the pump. It uses the price you type.
• It does not know the road: it has no map, it does not ask where you are, and it does not know about traffic, detours or a wrong turn.
• It counts gas only: no tolls, parking, oil, tires, repairs or insurance.
• It prints miles and gallons. The sums are the same with kilometers and liters, if every box uses the same pair: kilometers, kilometers on one liter, and the price of one liter.
• It is about gasoline for a car, not the gas in a home. A smell of gas indoors is a danger: 911 is the number for danger, and this page is no help with it.
• It never says whether to make a trip, or which way to go.
• It holds up to 20 counts on this device, and they do not move to another phone or computer by themselves.

If gas money is what stands in the way

• For a medical visit: Rides to care is our page about getting a ride to an appointment.
• Calling 211 reaches a local helpline in most of the U.S. that knows what help is near you.
• When money is short all around: Help with money.