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How To Estimate The Cost Of Gas For A Road Trip (Easy Calculations)

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This simple guide will explain step-by-step how to estimate the gas cost for your upcoming road trip. Use this gas cost estimator to establish how much money to put aside for fuel expenses so that you can focus on enjoying your adventure.

Planning a road trip takes time. Knowing how to calculate the gas cost of a road trip is an important part of the planning process. Forecast your expenditure and create a road trip budget by working out the costs using the price of gas and the estimated mileage per gallon of your vehicle.

The Quick Answer:

To estimate the cost of gas for your trip, perform the following calculation:

Divide the total distance of your trip by the miles per gallon of your vehicle. Take this number and multiply it by the price per gallon of gas ($). This figure will be the estimated cost of gas for your trip.

Estimated Cost Of Gas ($) = (Total Mileage / Vehicle MPG) x Gas Price ($) Per Gallon

You can also use our online Fuel Cost Calculator for an estimate.

how to estimate the cost of gas for a road trip
Gas Estimation Infographic

Now let’s do this step-by-step with a full explanation…

Estimate The Mileage Per Gallon Of Your Vehicle

The first step is to estimate the gas mileage, or miles per gallon, of your vehicle. The easiest way to do this is to visit the search tool and find your vehicle. You will then see the officially listed combined highway/city MPG figure, which you need to make a note of.

It’s important to note that gas mileage can be heavily influenced by driving style. If you want to calculate your personal gas mileage, use the following process: Fill up your tank and record the odometer reading. Next time you fill up your vehicle, take the new odometer reading and make a note of the number of gallons required to fill up the tank. Divide the miles driven in between gas station visits by the number of gallons required to fill the tank up. This figure will be the miles per gallon achieved in between gas station visits.

Calculate The Total Mileage Of Your Trip

When you are planning your road trip, it’s a great idea to use a free route planning tool. This will allow you to easily establish the total trip distance that you are expecting to drive. Make a note of this figure to be used later when estimating the cost of gas for your journey.

It’s important to make a note of how much distance is expected to be covered in city locations, as your fuel economy will worsen during this time. I will explain later in this article how to calculate a more accurate figure which takes city/highway mileage into account.

Find Out The Current Price Of Gas

If you visited the gas station recently, you may be aware of the current price. Find the cheapest gas station in your area and make a note of the price. If you are taking a long trip then it will make sense to fill up the tank at the cheapest location prior to departure.

Estimate The Total Cost Of Gas For Your Trip

By now, you should have written down your estimated miles per gallon (Mpg), total trip distance, and the price of gas. You are now ready to perform the calculation that will estimate the total cost.

Now Perform This Calculation To Estimate Gas Cost For Your Trip

Take the number of total miles and divide it by the estimated MPG of your vehicle. Next, multiply this number by the price of a gallon of gas in USD($). This will give you the estimated total cost in USD ($).

Estimated Cost Of Trip ($) = Total Mileage / Vehicle MPG ) x $ Gas Price/ Gallon

If you do not want to do this manually, another option is to use the Fuel Cost Calculator on the government website.

Adjusting The Estimation For City and Highway Mileage

The estimated MPG of your vehicle obtained from the Fuel Economy government website will usually be in the form of a combined city/highway figure. If you want a more accurate calculation you can adjust the estimation by calculating a separate figure for city driving and highway driving, then adding them together.

To do this you will need:

  • The city driving MPG and the highway mileage MPG figure from the Fuel Economy website.
  • The estimated city mileage and highway mileage figures expected to be driven
  • The price of gas in $ per gallon.

Simply follow the same process as in the previous step, but for city/highway mileage separately. Then add the two figures together to get the total estimated cost.

For a more accurate estimation of the cost of gas using city/highway mileage, perform the following calculation:

Estimated Cost Of Trip ($) = ((City Miles/ City MPG) + (Hwy Miles/ Hwy MPG)) x $ Gas Price/Gallon

Example Gas Cost Calculation

Example gas cost estimation using the combined city/highway MPG figure

  • You are planning a road trip with a total distance of 800 miles. The miles per gallon of your vehicle is 33, and the price of gas is $3.06 per gallon.
  • The gas cost estimation would be: (800/330) * $3.06 = $74.18

You can use this calculation when creating your Road Trip Budget.

Reducing The Gas Costs For Your Road Trip

Here are five quick steps for reducing the cost of gas for your road trip. More details can be found in our full post on saving money on gas on a trip.

  1. Drive sensibly by avoiding rapid acceleration, speeding, and braking.
  2. Observe the speed limit
  3. Avoid hauling excessive weight or roof cargo
  4. Avoid excessive engine idling (Check out our guide on how long you can leave a car running for more information on this)
  5. Use cruise control

Disclosure: Some of the links in this article may be affiliate links. This means I earn a commission if you make a qualifying purchase, but this is at no additional cost to you. Thank you for supporting The Road Trip Expert.

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Iain Salter

Founder & Editor of The Road Trip Expert

Iain founded The Road Trip Expert in 2019 and continues to manage the website to this day. The inspiration to start the blog came during an extensive road trip around Europe with two friends that spanned several months and involved over 25,000km of driving. He first developed a passion for backpacking in 2014 and has had the pleasure of exploring over 60 countries.