Trip Fuel Calculator
Estimate the gallons a trip will need.
Results update as you type.
How it works
Before a long drive it helps to know how much fuel the trip will actually swallow, and this trip fuel calculator gives that figure from two numbers you already know. Enter the distance you plan to travel and your vehicle's fuel economy in miles per gallon, and it returns the gallons the journey needs, so you can plan fuel stops and budget with confidence. Knowing gallons in advance is practically useful in several ways. It tells you whether a single tank will cover the route or whether you need to plan refuelling stops, which matters on remote stretches where stations are sparse. It also lets you multiply by the local fuel price to estimate the trip's cost, and it helps you pack the right expectations for how often you will pull over on a road trip with children or a schedule to keep. The math is deliberately simple: distance divided by miles per gallon equals gallons. Because MPG is the distance one gallon carries you, dividing your total distance by it counts how many gallons that distance consumes. For the most realistic estimate, use the fuel economy you actually observe rather than the optimistic window-sticker figure, since highway ratings assume ideal conditions. Loaded roof boxes, mountain grades, headwinds, and heavy traffic all raise consumption, so if your route is demanding, nudge the MPG down a little and the calculator will reflect the extra fuel you are likely to burn.
gallons = distance ÷ MPG
Miles per gallon states exactly how far your vehicle travels on one gallon of fuel, so dividing the trip distance by that figure reverses the relationship and returns the number of gallons required to cover the distance. The larger your MPG, the fewer gallons a given trip demands, and the longer the distance, the more fuel it needs. The calculation assumes steady real-world economy across the whole journey.
Source:U.S. EPA fuel economy
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter trip distance and fuel economy.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Gallons needed updates instantly as you type — no button to press.
Frequently asked questions
Which MPG figure should I use?
Use the fuel economy you actually achieve rather than the manufacturer's rating, since real-world driving rarely matches the lab test. If most of the trip is highway, a highway rating is reasonable; if it involves city traffic, hills, or heavy loads, use a lower figure. Tracking your MPG over a few tanks gives the most reliable number, and using it here produces a fuel estimate you can trust for planning.
Should I add a safety margin to the gallons?
It is wise to. The calculation assumes steady economy over the whole trip, but real conditions vary, and running a tank to empty is risky. Many drivers plan to refuel with a quarter tank remaining. Adding roughly ten to fifteen percent to the estimated gallons builds in a buffer for detours, traffic, terrain, and the difference between rated and actual economy, so you are unlikely to be caught short.
How do I turn gallons into a trip cost?
Multiply the gallons needed by the price per gallon you expect to pay. For example, 15 gallons at four dollars a gallon costs sixty dollars. If prices vary along your route, use an average or the highest likely price to stay on the safe side. A dedicated fuel cost calculator can do this in one step, combining distance, economy, and price into a total for you.
Will my actual fuel use match this estimate?
It will be close if your MPG figure is realistic, but expect some variation. Terrain, weather, traffic, air conditioning, cargo weight, and driving style all shift consumption, sometimes noticeably. Long climbs and headwinds increase fuel use, while steady highway cruising decreases it. The estimate is a solid planning baseline; for a long or remote trip, err on the side of carrying more fuel than the bare calculation suggests.
Does this work for electric vehicles?
This calculator is built for fuel measured in gallons, so it does not directly apply to electric cars, which measure energy in kilowatt-hours. To estimate an EV's needs, divide the trip distance by the car's efficiency in miles per kilowatt-hour to get the energy required. An EV range calculator is better suited to that task, since it accounts for battery capacity and efficiency rather than gallons of fuel.