How to estimate gas for a trip

An extensive and well-maintained interstate highway system makes road tripping in the U.S. both easy and enjoyable. But added expenses like gas and tolls can add up and surprise you if you don’t account for them. That’s why it’s a good idea to calculate the cost of gas for a trip ahead of time, especially if you’ll be on the road for a while or sharing expenses with others.  

You can use our calculator below to estimate gas expenses, but there are also things to keep in mind that may affect your overall gas usage and potential final cost. We’ll review an easy method to calculate the cost of gas specific to your trip itinerary and vehicle type, then dig into those key factors to remember.

Cost of gas for trip calculator

As you begin planning, it’s important to remember that calculating gas costs for road trips is truly just an estimate. If you encounter heavy traffic or find yourself cranking the AC more often, you’ll know that your estimate needs to increase a bit. Or if it’s smooth sailing, you may be able to pay less overall. Use the calculator below to estimate gas for a road trip:

As you see, you’ll need three different numbers to make the calculation: your car’s average fuel economy (expressed as mpg), the total number of miles you plan to drive and the average cost of a gallon of gas. To estimate the cost of gas, you first divide your driving distance by your car’s fuel economy, which will give you the number of gallons of gas your car will need to complete the drive. So if you’re driving 300 miles and your car gets 25 mpg, you will need 12 gallons of fuel. Then, multiple the number of gallons needed by the average price of gas to get your trip’s estimated fuel cost. For example, 12 x $2.68 equals $32.16. 

If you don’t know your car’s fuel economy or the average cost of a gallon of gas, you can quickly research those numbers online, or use the U.S. government’s fuel economy trip calculator, which provides estimates for you.

5 factors that affect fuel usage 

If your travel plans include hours on the road, it’s a good idea to estimate the cost of gas for your trip and build it into your budget. But before you drive off, you should know the key factors that affect how much gas you’ll use so you can cut back where possible. These five will heavily influence how much gas your car consumes during your trip, but there are many other contributing factors, including tire pressure, vehicle maintenance, cruise control usage and whether you’re running the air conditioning.

1. Fuel efficiency

Fuel efficiency is the measure of how a vehicle utilizes fuel, and it differs by make and model, while fuel economy refers to a specific estimated distance that a particular car can travel with a set amount of fuel, such as 25 miles per gallon (mpg). You can typically find your car’s fuel economy online or calculate this number yourself. It’s best to view this number as more of a guideline than a rule, as it will fluctuate based on external factors, such as vehicle weight, whether you’re running the air conditioning and if you’re driving on the highway versus in the city. Even so, this is the number you’ll use to estimate gas for a trip. 

2. Detours

Just because you set your origin and destination in your favorite GPS app and selected the most efficient route doesn’t mean it’s set in stone. You may run into unexpected construction or an accident that forces a detour or a long re-route in lieu of sitting in traffic. On the other hand, you may see a sign for an off-highway attraction — like Cadillac Ranch in Texas — and decide to check it out. And why not? That’s the fun of an American road trip! Of course, these additional miles will inevitably require more gas.

3. Speed

Your vehicle’s fuel efficiency will vary based on whether you’re spending long amounts of time cruising down the highway at a set speed versus continuously accelerating and decelerating due to traffic lights or speed limit variations. In general, maintaining a steady speed will help your car utilize fuel more efficiently, so opt for routes that keep you moving.

4. Terrain

Your car has to work harder when climbing hills or maneuvering switchbacks, so you’ll use more fuel in these instances versus on flat routes.

5. Weight 

A lighter car with, say, just you and a suitcase, will have higher fuel efficiency than if the car is loaded with additional passengers, camping gear and bikes strapped to the back.

3 ways to reduce fuel costs

Unforeseen circumstances, like getting stuck in stop-and-go traffic or being forced to take a detour, can derail your plan to optimize your route and fuel efficiency. Even if you need to burn more fuel, there are still ways to reduce your bill at the pump.

1. GasBuddy app 

This community-driven app is free on both the App Store and Google Play. Use it to find nearby gas stations, recent fuel prices and the best deals, and then route yourself to the station of your choice. You can also sign up for a free GasBuddy fuel card that will help you save at the pump too. 

2. Paying cash 

Swiping your credit card and driving off is easy and convenient, but if you have cash on hand then you may be able to save some cents per gallon. That’s because some gas stations offer a lower price to  those paying with cash versus a card. The discount can be significant in some cases, so if you’re comfortable with carrying cash in your wallet, then stop at the ATM before hitting the road.

3. Credit card offers

If you’d rather not pay with cash and want to rack up credit card reward points, then you may also be able to cash in on other card benefits. You’ll need to log in to your online account and see if you are able to add special offers to your card. These deals include a range of vendors, from hotels to clothing stores. You may see, for example, a 5% cash back offer for Shell gas stations. You’ll need to select each individual offer that you want added to your card. Then when you go to pay for gas at Shell, you will later find a statement credit equivalent to 5% of your bill total. Of course, there will be terms and conditions, such as a cap on the amount of money you can get back, so read the fine print of each offer.

Save more on transportation

Gas isn’t the only transportation-related expense that you can reduce during a long road trip. You can save a lot of money on a rental car too. If your trip starts in Chicago or Denver, then Avail car sharing is your best option. Each booking is protected by Allstate insurance and 24/7 roadside assistance, and Avail doesn’t charge extra to add a second driver to split the time behind the wheel. It’s also really easy to get on the road quickly with Avail since all pick-up locations are self-service and in convenient areas across each city. See how much you can save when you book with Avail.