What each price move costs you
Using the distance and fuel economy in the calculator. A rise and a drop of the same size move your bill by the same amount in opposite directions.
| Change per gallon | Per month | Per year |
|---|---|---|
| 10 cents | $4.00 | $48.00 |
| 25 cents | $10.00 | $120.00 |
| 50 cents | $20.00 | $240.00 |
| 75 cents | $30.00 | $360.00 |
| $1.00 | $40.00 | $480.00 |
Worked example: a 50-cent rise
- Fuel a month: 1,000 miles ÷ 25 MPG = 40 gallons
- At $3.50: 40 × $3.50 = $140 a month
- At $4.00: 40 × $4.00 = $160 a month
- Difference: $20 a month, or $240 a year
The price went up 14.3%, so the fuel bill went up 14.3% too. To spend the same $140 at the new price, you'd need to drive about 12.5% fewer miles, roughly 875 miles a month instead of 1,000.
How the price change is calculated
Change per month = (new price − old price) × gallons a month
Gallons a month is your monthly miles ÷ MPG. Yearly miles are divided by 12 and weekly miles multiplied by 52 ÷ 12 to get a monthly figure. The break-even mileage cut is 1 − old price ÷ new price, which keeps the monthly bill the same at the new price. When the price drops, that figure becomes the extra driving you could do for the same money.
Cedrick Reese built this page for anyone who sees the price at the station jump and wants to know what it means for their budget, not just the price per gallon. The math is the change in price times the fuel you actually buy, checked against the 50-cent worked example and the table above. The site never publishes current or forecast prices, so both prices are numbers you enter, and the price background comes from the U.S. Energy Information Administration. The car picker's EPA ratings are rebuilt from the fueleconomy.gov dataset whenever it's refreshed.
Gas price change questions
How much does a 50-cent rise in gas prices cost me?
Work out the gallons you buy in a month (miles ÷ MPG), then multiply by $0.50. Driving 1,000 miles a month at 25 MPG uses 40 gallons, so a 50-cent rise adds $20 a month, or $240 a year.
How much does a $1 increase in gas cost per year?
It adds $1 for every gallon you buy in a year. At 12,000 miles a year and 25 MPG you buy 480 gallons, so a $1 rise costs $480 a year. A 40 MPG car on the same miles buys 300 gallons, so the same rise costs it $300.
How many fewer miles would offset a price rise?
To keep your fuel bill the same, cut your miles by the same share the price went up, measured against the new price: 1 − old price ÷ new price. A rise from $3.50 to $4.00 needs about 12.5% fewer miles to break even.
Why do gas prices change?
The U.S. Energy Information Administration breaks the retail price into four parts: the cost of crude oil, refining costs and profits, distribution and marketing, and taxes. Changes in any of them move the pump price. EIA also notes that demand usually rises in summer, which generally results in higher prices.
Does better fuel economy protect me from price rises?
It shrinks them. A price rise costs you the change in price times the gallons you buy, so a car that uses fewer gallons for the same miles feels every rise less. Enter two different MPG figures with the same prices to see the gap.
More fuel tools
For your whole fuel budget at one price, use the gas budget calculator. If most of your driving is to work, the commute cost calculator adds parking and tolls.
A more efficient car is the long-term hedge against price swings. Compare fuel costs between two vehicles on our sister site, GasMileageCalculators.com.
If prices are climbing, how to save money on gas lists what actually helps, and the premium vs regular guide shows what the grade you buy costs.